Extreme Heat Warning vs Heat Advisory: What the Alert on Your Phone Actually Says About Your Animal

A heat alert tells you almost nothing about your animal. The National Weather Service (NWS) writes its Extreme Heat Warning, Extreme Heat Watch and Heat Advisory for people, and the only pet line in its model alert text is a warning not to leave pets in unattended cars. No NWS document we cite maps an alert level to an animal action, and this page does not invent one. Ask your veterinarian what heat your specific animal can take, and if an animal is already in trouble, call a veterinarian or emergency animal hospital now.

The phone buzzes on a Tuesday afternoon and the banner says Heat Advisory. Somewhere in the house there is a dog who expects a walk at five, a cat asleep in a west-facing room, a rabbit in a hutch on a concrete patio. The alert mentions none of them.

What this page can do is better than a made-up table. It shows which products exist now, which names were retired, who sets the trigger numbers, what those numbers measure, what the alert text says about animals, and where the veterinary evidence and the weather evidence meet.

If you are past decoding and into response, two pages own that ground. The dog heatstroke page covers signs, cooling and when to stop reading and drive. The heat wave and hot cars page covers parked cars, the never-do list and cooling gear.

The three products that exist now

NWS’s Understanding Heat Alerts page says each forecast office issues some or all of three heat products as conditions warrant, and that local offices often work with local partners to decide when an alert should be issued. It gives an example: residents of Florida are much more prepared for 90°F+ weather than residents in Alaska. NWS labels the Warning and the Advisory “Take Action” and the Watch “Be Prepared.”

• Extreme Heat Warning. Issued when extremely dangerous heat conditions are expected or occurring. NWS says to avoid outdoor activities, especially in the heat of the day; if you must be outside, drink plenty of water and take frequent breaks in the shade; stay in an air-conditioned space as much as possible, including overnight; and check on family and neighbors.
• Extreme Heat Watch. Issued when conditions are favorable for an extreme heat event but its occurrence and timing are still uncertain. NWS says to plan to suspend all major outdoor activities if a warning is issued, and, if you have no air conditioning, to locate the nearest cooling shelter or discuss staying with family or friends who have it.
• Heat Advisory. Issued for dangerous heat that is not expected to reach warning criteria. NWS says to consider postponing or rescheduling outdoor activities, especially in the heat of the day; drink water and take shade breaks if you must be outside; and stay in a cool place during the day and evening.

Three points from those descriptions:

• The ladder is not what most people assume. A Watch is not less bad than an Advisory. It is uncertainty about a Warning. NWS Instruction 10-515, the directive that governs these products, defines a Watch this way: “Conditions are favorable for an extreme heat event to meet or exceed local Extreme Heat Warning criteria in the next 24 to 72 hours.” By expected severity, a Watch outranks an Advisory. By certainty, the order reverses.
• Every instruction is addressed to a person. Drink water, take shade breaks, stay in air conditioning, check on neighbors, find a cooling shelter. Not one word is about an animal.
• None of the three descriptions contains a number. The trigger numbers are the next section.

Names that were retired, and where they still appear

Two names you may remember are gone. NWS Headquarters issued Service Change Notice 24-88 on Thursday, September 5, 2024, titled “Renaming of Excessive Heat Watch and Warning to Extreme Heat Watch and Warning: Effective March 4, 2025”. It replaced the Valid Time Event Code used for the old products, which is what automated weather feeds key on. NWS Instruction 10-515, dated May 16, 2025, records the same change.

So Excessive Heat Warning and Excessive Heat Watch are retired names for what these products were called before March 4, 2025. No NWS document cited here names a product called simply a Heat Watch. If a page offers you one, it is being loose with the name or describing something else.

Old names are still on screen. As of August 15, 2026, the NWS Green Bay office’s own heat page still described an Excessive Heat Watch and an Excessive Heat Warning/Advisory, and the Northeast threshold document cited below still refers to Excessive Heat Warning criteria. Neither is worthless, but both are stale in one specific way. Check a product name against the national Understanding Heat Alerts page, not the first local page a search returns. Treat an old product name as a date stamp: numbers on that page may have moved too, and they do move. One of the criteria sets below was revised weeks before this page was written.

What the alert text says about your animal

The public descriptions above say nothing about animals, but the alert itself is a text product a local office writes. NWS Instruction 10-515 publishes model examples in its Appendix A, which show what a heat alert puts in front of a household.

The wording NWS says goes in all of them. The directive says NWS and the Occupational Safety and Health Administration (OSHA) have agreed to include specific text in call-to-action statements in all NWS Heat Advisories and Warnings. It begins with a capitalized instruction to take extra precautions if you work or spend time outside, reschedule strenuous activity to early morning or evening when possible, know the signs and symptoms of heat exhaustion and heat stroke, wear lightweight, loose-fitting clothing and drink plenty of water. A second block covers rest breaks for outdoor work and ends by saying heat stroke is an emergency and to call 911. It is written about workers and human symptoms. There is no animal in it.

The model text for each product. Across the directive, the word pets appears twice, both times inside Appendix A’s model alert texts, and only one of the two is a heat product. In the model Extreme Heat Warning, the actions section says: “Do not leave young children and pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes.” That is the entire animal content of the model text for the most severe heat product NWS issues, and it is about a parked car.

Model text (NWSI 10-515, Appendix A)	Names an animal?	What it tells a household to do	OSHA worker block
Extreme Heat Watch	No	Drink fluids, stay in an air-conditioned room, stay out of the sun, check on relatives and neighbors	No
Extreme Heat Warning	Yes, once: the parked-car line above	The above, plus lightweight clothing, limiting strenuous activity to early morning or evening, and acting on symptoms	Yes
Heat Advisory	No	The human items above, plus monitoring later forecasts	Yes
Cold Weather Advisory (for contrast; not a heat product)	Yes: “Keep pets indoors as much as possible.”	Check on older family, friends and neighbors; use portable heaters correctly; no generators or grills inside	No

Two scoping notes. Appendix A publishes examples, and your local office writes the text it actually sends, so do not read the table as a promise about your phone. And none of this criticizes the products. They are meteorological hazard products, and their job is not veterinary advice.

Our reading, not an NWS statement: the heat alert system treats a companion animal as a passenger-in-a-hot-car problem and nothing else. If you are waiting for the alert to tell you something about your dog, it has already said all it will.

The trigger number is set by your own forecast office

There is no national number. NWS Instruction 10-515 defines an Extreme Heat Warning by heat index values forecast to meet or exceed locally defined warning criteria for at least two days, with typical values of a maximum daytime heat index of 105°F north to 110°F south and minimum nighttime lows of 75°F or higher. It defines a Heat Advisory by locally defined advisory criteria for one to two days, with typical values of a maximum daytime heat index of 100°F north to 105°F south and lows of 75°F or higher. The directive adds: “The Extreme Heat Warning/Heat Advisory criteria are highly variable in different parts of the country due to climate variability and the effect of extreme heat on the local population.” It encourages offices to set local criteria with local emergency and health officials. Anyone who publishes the typical values as “the criteria” and drops that note has handed you a number that is wrong somewhere.

Four criteria sets, none the same

Source	Heat Advisory criteria	Extreme Heat Warning criteria
NWSI 10-515, national directive (typical values only)	Maximum daytime heat index 100°F north to 105°F south; minimum nighttime lows 75°F or higher	Maximum daytime heat index 105°F north to 110°F south; minimum nighttime lows 75°F or higher
NWS La Crosse, WI	Daytime heat index of 100°F or higher expected; an advisory might also be considered if the heat index is 95° to 99°F for four or more days	Heat index of 105°F or greater with a minimum heat index of 75°F or greater for at least 48 hours; may also be issued when advisory criteria are met for four or more consecutive days
NWS Little Rock, AR (document states new criteria effective July 1, 2026)	Not addressed in this document	Maximum heat index above 110°F, or above 105°F combined with a minimum nighttime low above 80°F
Northeast Regional Heat Collaborative, northern New England and parts of New York (see caveat below)	Heat index of 95-104 degrees for 2 or more consecutive hours	Heat index values in excess of 105 degrees for 2 or more consecutive hours, stated under the retired name

In La Crosse, the published daytime trigger for an Advisory is a heat index of 100°F or higher. In northern New England, an advisory fires at 95°F held for two hours. In Little Rock, no Extreme Heat Warning comes until the heat index passes 110°F, or passes 105°F with an overnight low above 80°F. So a person in Maine can get an Advisory on an afternoon that would produce no product at all in parts of Arkansas. That is deliberate. The Northeast document explains that residents there are less physiologically adapted to extreme heat and buildings are not built to counteract it, and it reports that local deaths and emergency department visits increase significantly on days with a heat index of 95°F compared with 75°F. It names the collaborative as a working group of public health agencies in Maine, New Hampshire, Vermont and Rhode Island, supported by Brown University.

A currency caveat on the Northeast row. That document carries no date in its text and says its lowered advisory criteria are effective immediately. It still uses the retired Excessive Heat Warning name, so it predates March 4, 2025. It remains on a weather.gov address, but nothing in it says whether 95°F for two hours is still the trigger. We cite it to show that an NWS advisory threshold has been set that low somewhere, not as the number for any address.

The Little Rock document adds a footnote that HeatRisk and Wet Bulb Globe Temperature will be taken into account for heat headlines to recognize different vulnerabilities. So at least one office says in writing that other measures inform the decision. NWS La Crosse also defines its alerts in one line each: a Heat Advisory means people can be affected by heat if precautions are not taken, and an Extreme Heat Warning means some people can be seriously affected. The office that publishes its criteria most plainly also scopes the product to people most plainly.

Two clauses that move the trigger

• A forecaster can issue below criteria for impact. Section 6.2.2.3 of the directive gives an example: if a heat event will not meet warning criteria but it is early in the season or unusually warm at night, when impact will likely be high, then a Heat Advisory or Extreme Heat Warning might be warranted. Both triggers matter for a household with animals.
• Criteria are lowered when the power goes out. After a severe event such as high winds, severe thunderstorms or a derecho, the directive strongly encourages offices to lower their heat advisory and warning criteria and emphasize the impact of losing air conditioning. That describes the day the “air conditioning is on” plan fails. The heat emergency with no air conditioning page covers the room, thermometer and cooling work. The derecho pet safety plan covers the storm that causes such outages.

How to find your own office’s number

This takes about ten minutes on a day when nothing is happening.

1. Go to weather.gov and search your city, state or ZIP code. You land on your forecast office’s page, and its header names the office that issues your heat alerts.
2. Look on that office’s site for a heat page. Some publish their criteria openly; La Crosse and Little Rock do. Others may not.
3. If yours does not publish criteria, use its contact page. These are public offices, and asking for the local heat advisory and extreme heat warning criteria is an ordinary question.
4. Write the answer down next to your veterinarian’s number. It converts a word on your phone into degrees.
5. Re-check it every couple of years. Little Rock’s criteria changed on July 1, 2026. Northern New England’s threshold was lowered. These move.

This is the same problem as evacuation vocabulary, where words are set locally and do not translate between jurisdictions; see evacuation levels decoded for pet owners.

What a heat index measures

Both issued products are defined on heat index values. NWS’s Heat Forecast Tools page says the heat index is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature. It also states the limit: “Since heat index values were devised for shady, light wind conditions, exposure to full sunshine can increase heat index values by up to 15°F.” It adds that strong winds, particularly with very hot, dry air, can be extremely hazardous.

A dog walk happens in sun, often on asphalt, often at the hottest part of the day. The heat index is a shade number, and the animal is not in the shade.

The index the canine research uses

On the same NWS page, Wet Bulb Globe Temperature (WBGT) uses temperature, humidity, wind, solar radiation and other parameters, and NWS calls it a particularly effective indicator of heat stress for active populations such as outdoor workers and athletes. The peer-reviewed research on heat-related illness in dogs is written in WBGT, not heat index. The 2022 VetCompass study of UK dogs in the journal Animals says WBGT takes air temperature, radiant heat, humidity and windspeed into account to assess thermal stress.

That study does not give a safe limit. It reports that the median maximum daily WBGT when UK dogs presented with exertional heat-related illness was 16.5 °C, much lower than temperatures typically associated with exertional illness in US military working dogs (above 26.7 °C), and that the lowest maximum daily WBGT recorded for an event was 3.3 °C, an exertion-triggered case in winter. Those describe conditions in which dogs became ill. They are not safe limits, and reading them as limits inverts their meaning. The study states: “No formal guidelines exist for dogs training or working in hot environments.”

So the alert on your phone is built on a shade-scoped human comfort index, the dog research uses an index that includes sun, and no source we cite converts either into a threshold for a dog or a cat.

What is established about an animal that cools by panting

The mechanism. The VetCompass study says “Dogs rely on evaporative cooling through panting once their thermoregulatory set point has been exceeded”, and that ambient temperature, humidity and windspeed all influence the rate of cooling. Humidity is one of three named variables that set how fast a panting dog can shed heat, because evaporation into humid air is slower. A hot, humid, still afternoon is harder on a panting animal than a hot, dry, breezy one at the same temperature.

Who gets hurt worst. The same study found the risk of severe disease was greater “in situations where dogs could not escape the heat source (vehicular confinement)” and the risk of death was greater “for those dogs with reduced capacity to thermoregulate (older and brachycephalic dogs).” One category is about the environment, an animal that cannot leave the hot place. The other is about the animal: older, and flat-faced. See cooling gear for brachycephalic dogs for the equipment question.

The scale. The 2020 Scientific Reports study identified 395 confirmed heat-related illness events among 905,543 dogs under veterinary care in 2016.

Our reading, marked as ours. NWS says the heat index assumes shade and full sun can add up to 15°F. The dog research uses an index that includes sun. Joined together, the alert on your phone systematically describes conditions milder than a dog experiences standing on pavement at two in the afternoon. That is not a threshold and does not become one. It gives a direction: when unsure, the heat index understates the walk, so choose the earlier hour and the shaded route, and ask your veterinarian.

Early-season heat

Part of the idea that the first hot spell of the year is the dangerous one is real and published. Part is not.

What NWS does with time of year. NWS’s HeatRisk product considers time of year, including whether this is early-season heat that you likely have not become used to, and keys risk levels to CDC heat-health thresholds. The page notes HeatRisk is experimental and not supported 24/7. The directive’s impact-criteria clause says a Heat Advisory or Extreme Heat Warning might be warranted if it is early in the season or unusually warm at night. Both are scaled to people, not animals. The heat wave and hot cars page covers HeatRisk itself.

What the veterinary literature says. Purdue Extension’s Temperature Requirements for Dogs (VA-16-W, October 2016) says animals exposed to temperatures outside their thermoneutral zone should be acclimated first, and that “partial acclimatization in small animals can require from 10 to 20 days; full acclimatization takes 60 days (Johnson et al., 2006).” Purdue is a kennel and animal-care management publication rather than a weather document, and it reports those figures from Johnson et al. The 2022 VetCompass study reaches the same mechanism: acclimatisation can take weeks and requires increasing exertion in a hot environment. It describes the UK climate as one that can cause sudden exposure to high temperatures without a chance to acclimatise, and concludes UK dogs developed illness at relatively low temperatures compared with dogs from a country where acclimatisation is possible. That acclimatisation statement cites a human heatstroke review (Bouchama and Knochel, 2002). Veterinary researchers made that application in print, but the timescale traces back through human literature, not a canine measurement.

What it does not say. A December 2025 review in Frontiers in Animal Science states that “whether domestic dogs exhibit seasonal physiological adjustments to heat, analogous to those observed in cold acclimation, remains uncertain.” The review notes cold-side evidence is established and hedges the heat implication: dogs in temperate regions may face acute risks during short, intense heatwaves. The 2020 Scientific Reports study found no events in February, October or December, and “40% (158/395) of the incident cases were in July”, the year’s hottest month rather than its first warm one. That study lists dog acclimatisation among variables its model omits, so it is not evidence against acclimatisation either.

So this page says: acclimatisation takes weeks, an animal that spent months in cool weather has not had those weeks, and the first warm weekend arrives at an unprepared animal. It does not say the first heat event is worse than a hotter one later. Nobody has established that for dogs. Treat early-season heat as a real hazard on its own terms, and do not use it to relax about August.

This alert will probably not wake you up

NWS’s Wireless Emergency Alerts page lists the NWS warnings that send a WEA message to a phone: tsunamis, tornado, severe thunderstorm when the damage threat is destructive, flash flood when the damage threat is considerable or catastrophic, hurricane, typhoon, storm surge, extreme wind, dust storm and snow squall. As of August 15, 2026, no heat product is on it.

So an Extreme Heat Warning does not push an unsolicited alert to your handset through that channel. If you saw one on your phone, it came through a weather app, a local news alert or your county’s notification system. That does not mean nothing will reach you: the same page lists local emergencies requiring evacuation or immediate action among WEA message types, and those come from state and local authorities. County opt-in systems are normally separate from WEA and require sign-up; inland hurricane pet preparedness covers the WEA list in more detail.

If your plan for a hot weekend depends on somebody noticing in time, build the noticing yourself. A calendar reminder to check the forecast at a fixed hour is more reliable than an alert that will not arrive.

What the federal system publishes for pets and heat

The federal government publishes a fair amount about pets and heat. It does not connect any of it to the alert products or to a number.

• heat.gov, the interagency federal heat portal, has a real pet page, At Risk Pets and Service and Support Animals. It says extreme heat can be dangerous for pets and that “Animals can die within 15 minutes of heatstroke.” It warns that paved surfaces may become excessively hot and owners should avoid walking pets on overly hot surfaces. It also notes that reluctance to leave a pet behind while seeking medical care, or uncertainty about whether a pet will be accepted at a cooling center, could cause owners to remain in a hot building when it is unsafe. Its instruction: “As a precaution, consider calling cooling centers well in advance of heat waves or heat season to determine if those nearest you will accept pets.” That is a calm-afternoon task; pets at cooling and warming centers covers it. The page does not mention heat index, HeatRisk or advisory.
• NWS’s own two pet heat pages (the Weather-Ready Nation article on keeping pets cool, and Children, Pets and Vehicles) do not use the phrase heat index.
• NWS’s Heat Safety Resources page names four groups as particularly vulnerable to heat: young children and infants, older adults, people with chronic medical conditions, and pregnant women. All are people. Its only pet content is that it is never safe to leave a child, disabled person or pet locked in a car, even in winter.
• CDC’s Heat and Pets page (dated June 25, 2024) tells owners never to leave a pet in a parked car and to leave plenty of fresh water in a shady area. For a number, it sends readers to the CDC HeatRisk Dashboard, which is the human product. Its only Fahrenheit figure is that temperatures inside a car can rise almost 20 degrees within the first 10 minutes even with a window cracked. It contains no heat index value and none of the words advisory, warning or threshold. HeatRisk is keyed to CDC heat-health thresholds, so the federal document likeliest to join a threshold to an animal does not.

Animals appear on all four surfaces. A weather number attached to an animal appears on none. The only sentences that pair a number and an animal are elapsed time (15 minutes) and a water-intake guideline quoted from a volunteer, not from NWS.

A note on NWS’s fullest pet heat page

The Weather-Ready Nation article “Keep Your Pets Cool During the Dog Days of Summer” is the longest and most practical pet page on weather.gov, and the one a search is most likely to surface. The page says its content came from the leader of a Louisa, Virginia Community Animal Response Team, a non-profit focused on preparedness for pets and their owners. That is legitimate practical experience. Its pavement check is the version many people know: “Place the back of your hand on the asphalt - if it’s too hot for you, it’s too hot for them.” But hosting on a federal site is not federal authorship, and it is not veterinary authorship. At least one nutritional claim on it is presented without any source. Weight it accordingly, and do not cite it as if NWS had made a veterinary statement.

No source cited here publishes a heat index cutoff for a dog. If a page offers you one, check who published it and whether it names a source.

What to do when one of these lands

Read the alert for what it contains. A heat product tells you what (a forecast heat index band), where (named counties), when (a start and end time) and impacts. The operational parts for a household are the timing and the overnight low. The timing tells you which hours to move things out of. The overnight figure tells you whether the house cools before tomorrow. A two-day event with no overnight relief is a different problem from a hot afternoon.

Do not look for the animal instruction in it. The one animal line in the model text is about a parked car. If another page hands you an Advisory-means-this, Warning-means-that rule, it is publishing its own rule, not NWS’s. Check whether it says so and whose reasoning it is.

Make the animal decision from the animal. The risk factors the VetCompass study identified are properties of the dog and its situation: an animal that cannot escape the heat source, an older animal, a flat-faced animal. If you have one, your plan changes at a lower bar than for a healthy young animal with a long muzzle, whichever word appeared on your phone. What that bar is, in degrees, is a conversation with your veterinarian, who knows the airway, weight, heart and medication list. No forecast page does.

If an animal is already in trouble, stop reading forecasts. Heavy panting, thick drool, unsteadiness, collapse, or abnormal gum or tongue color are emergency signs. Call your veterinarian or the nearest emergency animal hospital immediately. The dog heatstroke page covers the signs and what to do before you arrive.

If smoke arrives too. Heat season and wildfire smoke season overlap. A smoke advisory pushes you to keep the animal indoors with windows shut, while a heat alert in a house without air conditioning is exactly when shutting windows is dangerous. EPA’s fact sheet Protect Yourself From Smoke and Heat says you may need to allow smoke inside while using night air for cooling, and that both are harmful but “for most people, heat is more immediately dangerous.” That is about people, not animals. Do not settle the conflict from this page; see the AQI and dog walking page and heat emergency with no air conditioning.

Your heat alert checklist

• Read the alert’s timing and overnight figure first. The hours covered and whether the night brings relief change what a household does.
• Check the product name against NWS’s Understanding Heat Alerts page. There are three: Extreme Heat Warning, Extreme Heat Watch, Heat Advisory. Excessive Heat Warning and Excessive Heat Watch were retired effective March 4, 2025.
• Remember the ladder: a Watch means a Warning may come in 24 to 72 hours (NWS: Be Prepared). An Advisory is lower severity (NWS: Take Action).
• Do not look for a pet instruction in the alert. In the model texts, only the Extreme Heat Warning names an animal, and it is the parked-car line.
• Find your forecast office’s heat criteria on a calm day and write them next to your veterinarian’s number.
• Treat the heat index as a shade number. Full sunshine can add up to 15°F.
• Rank your animals by the published risk factors, not by the alert level: an animal that cannot leave the hot place, an older animal, a flat-faced animal.
• Do not plan on the alert waking you. Set your own forecast check and sign up for your county’s notification system.
• If the power goes out during a heat event, expect criteria to be lowered and expect your own plan to be what failed.
• Call cooling centers before heat season and ask whether they admit animals.
• Do not accept a heat index cutoff for a dog from any page that does not name its source.
• If an animal shows heat illness signs, call your veterinarian or the nearest emergency animal hospital now.

The version you do on a cool afternoon

Almost everything here is more useful in April than in July.

• Settle the numbers question once. Find your forecast office and its criteria and write them down. After that, every alert converts from a word into a range of degrees.
• Have the veterinary conversation at a routine appointment. The question is not what temperature is too hot for a dog in the abstract. Purdue notes that age, breed, health and acclimation all matter, but that there are no recommendations or much scientific data giving appropriate temperature ranges by those factors. Ask instead: for this animal, with this airway, heart and weight, what should change on a hot day, and which signs should I not wait on?
• Build the acclimatisation gap into the calendar. The published timescales are weeks. When the season turns, the animal has not turned with it.
• Solve the cooling-center question in advance, which is heat.gov’s own advice.
• Write down one page: your forecast office’s name, its heat criteria, your veterinarian’s number and your nearest emergency animal hospital’s number, somewhere someone who is not you could find it.

Where to go next

This page is the alert-decoding spoke of the pet emergency playbooks hub.

• The heat is already here: heat wave and hot cars.
• An animal is in trouble now: dog heatstroke.
• The air conditioning is gone: heat emergency with no air conditioning.
• Smoke and heat together: AQI and dog walking.
• The word on your phone is an evacuation word: evacuation levels decoded.

Then do the one thing that pays off most. Open weather.gov, enter your ZIP code, find the office that will issue your alerts, and find out what heat index number sets them off.