Extreme summer heat is becoming a broader public-safety problem across the United States, with new data showing the greatest risks concentrated across the South and Sun Belt.
A nationwide analysis by Texas Law Dog ranked all 50 states according to daytime and nighttime temperatures, persistent heat, unusually warm conditions and population vulnerability. Florida ranked first nationally, with a Heat-Danger Index score of 84.5 out of 100, narrowly ahead of Arizona at 84.4 and Louisiana at 84.0. Texas followed in fourth place with a score of 81.7.
The findings come as prolonged heat increasingly affects health, workplaces and transportation across the country. Federal climate data show that unusually hot summer days have become more common, while unusually warm nights have increased even faster. Major U.S. cities now experience roughly six heat waves per year, compared with around two annually during the 1960s.
The States Facing the Greatest Summer Heat Risk
Texas Law Dog’s ranking found that the states facing the greatest combined heat risks are overwhelmingly concentrated in the southern United States.
| Rank | State | Heat-Danger Index |
|---|---|---|
| 1 | Florida | 84.5 |
| 2 | Arizona | 84.4 |
| 3 | Louisiana | 84.0 |
| 4 | Texas | 81.7 |
| 5 | Mississippi | — |
| 6 | Arkansas | — |
| 7 | Oklahoma | — |
| 8 | Alabama | — |
| 9 | South Carolina | — |
| 10 | Georgia | — |
Florida’s position at the top was driven in part by consistently hot nights. The state recorded an average summer minimum temperature of 73.8°F, limiting nighttime relief following high daytime temperatures.
Arizona, meanwhile, recorded the country’s highest average summer daytime temperature at 95.7°F. Its grid cells averaged 33.5 summer days at or above 100°F and 6.2 days at or above 110°F, the highest figures recorded in the study.
Texas ranked fourth overall but recorded the highest five-year average summer maximum temperature, at 95.2°F between 2021 and 2025.
The ranking reflects a broader trend in federal climate records. NOAA reported that the contiguous United States had an average temperature of 75.4°F in July 2025, or 1.8°F above the 20th-century average. Twelve states recorded their warmest average July minimum temperatures on record, highlighting the increasing importance of overnight heat.
Heat Waves Are Becoming More Frequent and Lasting Longer
Extreme heat is no longer limited to isolated record-setting days.
EPA climate indicators show that major U.S. cities now experience an average of approximately six heat waves per year, compared with about two during the 1960s. The average heat-wave season has also expanded substantially and is now roughly 46 days longer than it was six decades ago.
Individual heat waves in major urban areas now last about four days on average.
That trend matters because repeated exposure increases the risk to people who lack reliable cooling or spend large portions of the day outdoors.
Warm nights can also amplify the effects of daytime temperatures by reducing the body’s opportunity to cool and recover.
This helps explain why the Texas Law Dog analysis weighted both daytime and nighttime heat. Daytime heat represented 30% of the final index, while nighttime heat represented another 20%. Persistent five-year heat accounted for 20%, unusual 2025 warmth for 10%, and population vulnerability accounted for the remaining 20%.
More Than Half of Hot-Car Deaths Occurred in the Highest-Risk States
One of the clearest consequences of prolonged heat can develop inside a parked vehicle.
The 10 states ranked highest for summer heat risk accounted for 531 of the 1,038 child hot-car deaths recorded between 1998 and 2025, or approximately 51.2% of the national total.
The five highest-ranked states alone accounted for 378 deaths.
| State | Child Hot-Car Deaths, 1998-2025 |
|---|---|
| Texas | 155 |
| Florida | 115 |
| Arizona | 46 |
| Georgia | 43 |
| Louisiana | 39 |
| Alabama | 34 |
| Oklahoma | 31 |
| South Carolina | 25 |
| Mississippi | 23 |
| Arkansas | 20 |
Population-adjusted comparisons show an even larger divide.
The 10 states with the highest heat-index scores averaged 33.7 hot-car deaths per 1 million children age 14 and younger, compared with an average of 8 per million among the 10 lowest-ranked states. That puts the average rate in the highest-risk group at more than four times the rate among the lowest-ranked states.
Federal transportation data confirm that vehicular heatstroke remains a persistent danger. The National Highway Traffic Safety Administration reported 31 child heatstroke deaths in vehicles during 2025. More than 1,000 children have died in hot vehicles over the past 25 years, while 2018 and 2019 each recorded 53 deaths.
Heat-Related Emergency Room Visits Spike During the Hottest Months
The public-health effects of extreme temperatures extend far beyond hot vehicles.
CDC surveillance identified 119,605 emergency department visits for heat-related illness during 2023, with 92% occurring between May and September.
The heat-related emergency department visit rate was much higher during July and August, averaging 303 visits per 100,000 emergency department visits, compared with 97 during May, June and September.
Men experienced substantially higher rates than women, at 271 versus 104 heat-related visits per 100,000 emergency department visits.
Working-age adults were also among the most affected groups. Adults ages 18 to 64 recorded substantially higher rates than children and adolescents during the CDC’s analysis.
Geography also matters. Texas Law Dog’s analysis highlighted particularly high heat-related health burdens across parts of the South and Southwest, where prolonged temperature exposure can coincide with large outdoor-work populations.
Vulnerability Can Matter as Much as Temperature
A state’s temperature alone does not determine the potential consequences of extreme heat.
Texas Law Dog included three vulnerable groups in its analysis:
- Children younger than 5
- Adults age 65 and older
- Workers in natural resources, construction and maintenance occupations
South Dakota recorded the highest population vulnerability score, at 76.2, even though its milder temperatures placed it much lower in the overall heat ranking.
Individual demographic measures also varied considerably. Utah had the largest share of children under 5, while nearly one-quarter of Maine’s population was age 65 or older. Wyoming had the country’s highest share of outdoor workers, at 14.4%.
Those differences demonstrate why a state with comparatively moderate temperatures can still have a substantial population exposed to heat-related health risks.
Outdoor Workers Face Some of the Most Direct Exposure
Extreme heat is also an occupational risk.
Workers in construction, agriculture, landscaping, utilities, transportation and other physically demanding jobs may spend hours outside during peak daytime temperatures.
The Texas Law Dog analysis cited federal labor data showing 48 occupational heat deaths in 2024, including 40 that occurred outdoors. Construction accounted for 24 of the 48 fatalities.
Longer-term data also show the scale of the issue. The Bureau of Labor Statistics recorded more than 1,000 worker heat deaths between 1992 and 2022, while tens of thousands of heat-related workplace illnesses have resulted in employees missing work.
Arkansas, Oklahoma, Louisiana, Texas, Illinois and Arizona were among the states identified as having particularly high construction-worker heat fatality rates in data reviewed for the study.
The Hottest States Do Not Always Have the Strongest Protections
Texas Law Dog’s findings also highlight differences between heat exposure and heat preparedness.
Among the states ranking in the top 10 for summer heat danger, none had adopted a broad statewide enforceable heat standard for workers at the time of the study.
Other states, including California, Maryland, Minnesota, Nevada, Oregon and Washington, had implemented comprehensive heat standards, while Colorado had protections targeting agricultural workers.
The gap illustrates an important distinction in the data: the states experiencing the greatest heat exposure are not necessarily those with the most extensive protections in place.
How the Heat-Danger Index Was Calculated
Texas Law Dog created its 50-state ranking using five components:
| Component | Weight |
|---|---|
| 2025 average summer maximum temperature | 30% |
| 2025 average summer minimum temperature | 20% |
| 2021-2025 average summer maximum temperature | 20% |
| 2025 maximum-temperature anomaly | 10% |
| Population vulnerability | 20% |
Each metric was converted to a state percentile before being combined into an overall score from 0 to 100.
The ranking is comparative rather than predictive. A score of 84.5 for Florida, for example, does not indicate an 84.5% probability of a heat-related illness or death. Instead, it reflects how the state’s combination of temperatures and population vulnerability compares with conditions in the rest of the country.
Taken together, the findings from Texas Law Dog show a pronounced geographic divide in America’s summer heat burden.
Florida ranked highest overall because persistent daytime and nighttime heat combined with population vulnerability, while Arizona recorded the most extreme daytime conditions. Texas, meanwhile, had the highest five-year average summer maximum temperature and the largest number of child hot-car deaths among the states examined.
As hotter days and warmer nights become more common, federal health and climate data suggest the consequences are extending well beyond uncomfortable summer weather. Emergency department visits, worker exposure, hot-car deaths and prolonged periods without nighttime relief increasingly make extreme heat a public-safety issue across much of the country.