Heat Season: When It Gets Hot, and How Long It Stays
The first 90 degree day, the last one, the days that clear 100, and the nights that never fall below 75, for all 50 states. Thirty years of NOAA records, plus live National Weather Service heat products read the moment you open the page.
Thirty years of NOAA climatology, plus live National Weather Service heat productsActive National Weather Service heat products
Read live from api.weather.gov when this page loads, and shown exactly as the issuing office wrote it. The National Weather Service uses three heat products as of 2025: Extreme Heat Warning, Extreme Heat Watch and Heat Advisory. The older Excessive Heat Warning and Excessive Heat Watch names were retired, so anything still using them is out of date.
Checking api.weather.gov for active heat products.
Product text, issuing office, area and times are passed through exactly as the National Weather Service issued them. As of 2025 the NWS uses three heat products: Extreme Heat Warning, Extreme Heat Watch and Heat Advisory. Read . Source: api.weather.gov
How hot each state gets, and for how long
Sorted by the number of 90 degree days at each state's primary reference city, which is the fastest way to see that this is not one national story. The day counts are quoted from NOAA's published 1991 to 2020 normals. The first 90 F dates and the warm night counts are our own derivation from NOAA daily observations over the same 30 years, because NOAA publishes no date shaped heat normal and no warm night threshold above 70 F.
| State | Reference city | Days 90 F or hotter | Days 100 F or hotter | First 90 F day | Nights 75 F or warmer | Page shape |
|---|---|---|---|---|---|---|
| Arizona | Phoenix | 173 | 111 | April 4 | 113 | Routine |
| Nevada | Las Vegas | 137 | 78 | April 19 | 85 | Routine |
| Texas | Dallas-Fort Worth | 106 | 20 | May 6 | 62 | Routine |
| Florida | Miami | 91 | 0 | April 4 | 142 | Routine |
| Louisiana | New Orleans | 85 | 0.3 | May 15 | 75 | Routine |
| Mississippi | Jackson | 85 | 3 | May 15 | 13 | Routine |
| South Carolina | Columbia | 81 | 6 | May 4 | 17 | Routine |
| Arkansas | Little Rock | 76 | 7.5 | May 20 | 25 | Routine |
| California | Sacramento | 76 | 14 | May 6 | 0.1 | Routine |
| Oklahoma | Oklahoma City | 73 | 13 | May 10 | 13 | Routine |
| Alabama | Birmingham | 65 | 2.4 | May 25 | 12 | Routine |
| Kansas | Wichita | 65 | 12 | May 30 | 12 | Routine |
| New Mexico | Albuquerque | 64 | 2.6 | May 27 | 0.5 | Routine |
| Utah | Salt Lake City | 62 | 7.6 | May 31 | 4.2 | Routine |
| Idaho | Boise | 55 | 9.1 | May 31 | 0.8 | Routine |
| Tennessee | Nashville | 54 | 1.1 | June 1 | 7.5 | Routine |
| North Carolina | Raleigh | 52 | 2 | May 19 | 4.4 | Routine |
| Georgia | Atlanta | 47 | 0.9 | June 1 | 9.8 | Routine |
| Missouri | St. Louis | 47 | 2.9 | May 18 | 21 | Routine |
| Virginia | Richmond | 45 | 1.6 | May 17 | 5.3 | Routine |
| Kentucky | Louisville | 43 | 1 | June 5 | 12 | Routine |
| Colorado | Denver | 42 | 1.5 | June 3 | 0 | Routine |
| Maryland | Baltimore | 34 | 1.3 | May 20 | 4.4 | Routine |
| Nebraska | Omaha | 33 | 1.6 | May 16 | 6.4 | Routine |
| Montana | Billings | 32 | 2 | June 8 | 0 | Routine |
| Hawaii | Honolulu | 32 | 0 | July 6 | 94 | Routine |
| Pennsylvania | Philadelphia | 30 | 0.5 | May 29 | 10 | Countable |
| New Jersey | Newark | 28 | 1.4 | May 25 | 8.9 | Countable |
| West Virginia | Charleston | 24 | 0.2 | May 31 | 0.4 | Countable |
| Delaware | Wilmington | 22 | 0.3 | May 30 | 4.8 | Countable |
| Iowa | Des Moines | 22 | 0.7 | June 6 | 4.2 | Countable |
| Ohio | Columbus | 21 | 0.2 | June 10 | 1.5 | Countable |
| North Dakota | Bismarck | 21 | 2.1 | June 13 | 0.2 | Countable |
| Indiana | Indianapolis | 20 | 0.4 | June 18 | 2.6 | Countable |
| Connecticut | Hartford | 20 | 0.4 | May 22 | 0.5 | Countable |
| New York | New York City | 17 | 0.5 | June 1 | 8.8 | Countable |
| Illinois | Chicago | 17 | 0.3 | June 6 | 2.6 | Countable |
| South Dakota | Sioux Falls | 15 | 0.6 | June 4 | 2.2 | Countable |
| Wyoming | Cheyenne | 15 | 0 | June 28 | 0 | Countable |
| Oregon | Portland | 15 | 1.3 | June 11 | 0 | Countable |
| Massachusetts | Boston | 14 | 0.1 | June 7 | 2.7 | Countable |
| New Hampshire | Concord | 14 | 0.1 | May 26 | 0.1 | Countable |
| Michigan | Detroit | 13 | 0.2 | June 11 | 1.2 | Countable |
| Minnesota | Minneapolis | 13 | 0.2 | June 2 | 2.1 | Countable |
| Rhode Island | Providence | 12 | 0.3 | June 9 | 1.4 | Countable |
| Wisconsin | Milwaukee | 9.1 | 0.2 | June 14 | 1.8 | Countable |
| Vermont | Burlington | 8.2 | 0.1 | June 18 | 0.7 | Countable |
| Maine | Portland | 5.1 | 0 | June 18 | 0.1 | Countable |
| Washington | Seattle | 3.8 | 0.1 | July 15 | 0 | Countable |
| Alaska | Anchorage | 0 | 0 | No median date | 0 | Rare |
Why the last column exists. A 90 degree day means something completely different in Phoenix than in Portland, Maine, so the state pages do not all lead with the same number. Which shape a state gets is decided by its data, not by editorial taste.
Routine
states whose primary city clears 90 F on 30 days a year or more. Ninety is the shape of July here, not an event, so those pages lead with season length, 100 F counts and overnight lows.
Countable
states where 90 F happens in most years but stays countable. The first and last 90 F day are real calendar markers people notice, so those pages lead with the window.
Rare
states (Alaska) whose primary city reaches 90 F in fewer than 50 percent of years, so those pages lead with cooling degree days, records and warm nights rather than a first 90 F date.
Hot days get counted. Hot nights are what matter.
Search for heat climatology and you will find days above 90 counted a dozen ways. You will almost never find nights counted, and the overnight low is the half of the day that decides what a hot spell actually does. Buildings shed stored heat overnight. Air conditioning gets its only break overnight. A 98 degree afternoon followed by a 68 degree night is a different event from a 94 degree afternoon followed by a night that never leaves the 80s.
So every state page here counts nights whose low never fell below 75 F. NOAA's published normals stop at 70 F, so that count is this site's own derivation from NOAA's daily minimum temperatures over the same 30 years as every quoted normal here, labelled as such wherever it appears. The highest count in this dataset belongs to Miami, Florida, at about 142 such nights a year.
Heat leads the National Weather Service's own fatality table
The NWS keeps a running tally of US weather fatalities by hazard. In its published ten year averages, heat sits at the top, ahead of flooding and well ahead of the hazards that get far more coverage. Those are the agency's figures.
| Hazard | 10 year average US fatalities a year | Share of the largest |
|---|---|---|
| Heat | 279 | 100% |
| Flood | 118 | 42% |
| Rip current | 76 | 27% |
| Wind | 57 | 20% |
| Tornado | 51 | 18% |
| Cold | 35 | 13% |
| Winter storm | 27 | 10% |
| Hurricane | 25 | 9% |
| Lightning | 19 | 7% |
The figures above are the ten year average column of the National Weather Service's 81 year US hazard summary, read in August 2026. They count deaths the NWS attributes directly to each hazard. Public health researchers generally treat direct counts like these as an undercount for heat specifically, because heat more often worsens an existing condition than appears alone on a death certificate.
Our summary of information published by NWS Weather Related Fatality and Injury Statistics
That is why these pages carry the climatology and the agency's own products, passed through unchanged, and route health questions to the National Weather Service and the CDC rather than scoring anyone's afternoon.
What the agencies say, in their own words
The heat index is an NWS product; where one appears on a state page, it is the value the National Weather Service published for that gridpoint. Two quotes worth having in front of you, the second more often left out than any other fact about heat:
National Weather Service, Heat Forecast Tools“The Heat Index is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature.”
National Weather Service, Heat Forecast Tools“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. Also, strong winds, particularly with very hot, dry air, can be extremely hazardous.”
Heat and health: the agencies, in their own words
Health guidance on heat comes from the National Weather Service and the CDC. Their words are below, and their full guidance is linked.
The National Weather Service on who heat affects: “Heat can be very taxing on the body and can lead to heat related illnesses or make existing health conditions worse. Everyone can be vulnerable to heat, but some more so than others.” (National Weather Service, Heat Safety Tips and Resources)
The CDC on knowing when something is wrong: “If your body gets too hot, you can get sick. Know the symptoms of your body overheating and know when to seek medical care.” (CDC, About Heat and Your Health)
Full guidance: NWS heat safety and CDC Heat and Health. The CDC also runs a CDC HeatRisk Dashboard for forecast heat by ZIP code.
CDC, About Heat and Your Health“Check on your family, friends, and neighbors, especially if they have chronic medical problems or live alone. Check on pets.”
Two registers, kept apart
Quoted from NOAA: days a year at or above 90 F, days at or above 100 F, cooling degree days by month and year, and nights below 70 F. All four are published variables in NOAA NCEI's 1991 to 2020 U.S. Climate Normals and are printed here untouched.
Derived by us: the median first and last 90 F day and their early and late percentiles, the season span, and the count of nights at or above 75 F. NOAA publishes nothing date shaped for heat and nothing above 70 F for nights, so those come from NOAA NCEI GHCN-Daily station observations over the same 30 years, computed by scripts/fetch-heat-season-stats.mjs and committed as a snapshot. Years under 85 percent reporting are excluded rather than filled in, readings that failed NOAA's own quality checks are skipped, and a percentile that lands on a year with no 90 F day prints nothing rather than a fabricated date.
Passed through verbatim: National Weather Service heat products, with the issuing office, the areas named, and the times, exactly as issued. Never done here: a heat index of our own, a risk score, or any statement about whether a given person is safe.
Sources: NOAA NCEI 1991-2020 U.S. Climate Normals, NOAA NCEI GHCN-Daily, NWS api.weather.gov. All are US Government works and in the public domain.
Heat season FAQ
Heat season, state by state
The same summer, other hazards
Day counts and cooling degree days quoted from NOAA NCEI 1991-2020 U.S. Climate Normals. Dates, season spans and warm night counts derived by us from NOAA NCEI GHCN-Daily observations over the same period. Live products from the National Weather Service, shown verbatim. For heat health guidance, see NWS heat safety and CDC Heat and Health.