Extreme heat is creating a growing transportation problem across the United States, with some states facing a particularly difficult combination of persistent high temperatures, deteriorating pavement and heavy traffic.
A nationwide analysis by Attorney Brian White ranks Arizona as the state facing the greatest heat-related driving risk, with an index score of 88.83 out of 100. Louisiana ranks second at 80.69, followed by Texas at 79.68.
The analysis examines more than temperature alone. It combines summer heat with road use and pavement conditions to identify where motorists are most exposed to conditions that can contribute to damaged roads, vehicle problems and potentially more dangerous crashes.
Arizona’s position at the top is supported by some of the most extreme summer conditions in the country. The state recorded an average summer maximum temperature of 95.79°F, the highest in the analysis, along with 80 statewide days reaching at least 90°F and 21 days reaching at least 100°F. Arizona was the only state to record a double-digit number of statewide 100°F days.
Arizona, Louisiana and Texas Face the Greatest Combined Heat Risk
The three highest-ranked states reached the top for somewhat different reasons.
Arizona’s score is driven primarily by the severity and persistence of its heat. Texas also stands out for prolonged high temperatures, while Louisiana’s position reflects a stronger combination of heat, traffic exposure and poor pavement.
| Rank | State | Heat-Related Driving Risk Score |
|---|---|---|
| 1 | Arizona | 88.83 |
| 2 | Louisiana | 80.69 |
| 3 | Texas | 79.68 |
Texas recorded the second-highest average summer maximum temperature at 93.45°F and the second-highest number of statewide 90°F days, at 78. Along with Mississippi, Texas also experienced the country’s longest uninterrupted period of 90°F-or-hotter conditions, lasting 43 days.
Louisiana ranked slightly higher overall despite experiencing less severe heat than Texas. One reason is pavement quality. 16.1% of Louisiana’s arterial pavement was classified as poor, compared with 7.3% in Texas, increasing Louisiana’s vulnerability when high temperatures are layered onto existing infrastructure problems.
Florida also placed among the highest-risk states. It recorded an average summer maximum temperature of 92.07°F, experienced 76 statewide days at or above 90°F, and endured a 35-day continuous stretch of 90°F-plus weather.
At the other end of the ranking, North Dakota recorded the lowest overall score at 13.56, followed by Minnesota at 13.67 and Wyoming at 18.56. Their lower rankings reflect substantially less sustained heat and lower combined exposure across the other measures.
Poor Pavement Can Make Extreme Heat More Damaging
Road condition is a major part of the risk equation because high temperatures can amplify existing pavement weaknesses.
When pavement heats and expands, roads can develop rutting, cracking, buckling and other forms of deterioration. Roads already weakened by age, moisture or traffic loads can be particularly susceptible.
Attorney Brian White’s analysis found that Rhode Island had the highest share of poor pavement, at 31.3%, followed by:
- California: 27.0%
- Massachusetts: 24.5%
- New Jersey: 18.5%
- New Mexico: 18.2%
Yet Rhode Island ranked only 29th overall, illustrating why poor road quality by itself does not create the highest heat-related driving risk.
California presents a stronger overlap between heat and infrastructure problems because it appears among both the states with higher overall heat exposure and those with the greatest shares of poor pavement.
Research cited in the analysis also demonstrates how dramatically heat can affect pavement performance. A 2025 study found modeled pavement rut depth increased from approximately 4 millimeters at 34°C to 8 millimeters at 49°C, before reaching roughly 13 millimeters at 63°C.
Houston Roads Offer a Real-World Example of Heat Damage
Texas provides a particularly visible example of how extreme heat can disrupt transportation infrastructure.
During a two-week period of high temperatures, the Texas Department of Transportation reported heat-related damage affecting at least 10 roadways in the Houston area.
Affected locations included an Interstate 10 entrance ramp, Highway 6 near Alvin and a section of Highway 146 in Baytown that required emergency overnight repairs.
Elsewhere in Texas, TxDOT identified 788 roadway miles in its Laredo District as highly vulnerable to extreme heat. Those miles represented more than half of the state’s road mileage identified as highly vulnerable in the data cited by the analysis.
Potential effects include:
- Pavement rutting
- Cracking
- Buckling
- Temporary road closures
- Detours
- Broader traffic disruptions
The findings show how extreme temperatures can create transportation problems even without directly causing a collision.
Heavy Traffic Adds Another Layer of Exposure
Traffic intensity can magnify heat-related roadway problems by placing more vehicles on vulnerable road networks.
Attorney Brian White measured traffic exposure using vehicle miles traveled per lane-mile.
New Jersey ranked first under that measure at 937,163 vehicle miles traveled per lane-mile, followed by:
| State | Vehicle Miles Traveled per Lane-Mile |
|---|---|
| New Jersey | 937,163 |
| Florida | 891,656 |
| California | 821,885 |
| Maryland | 795,063 |
| Massachusetts | 794,675 |
New Jersey’s high traffic exposure was not enough to push it toward the top of the overall heat ranking. It placed 18th overall, reinforcing the importance of considering traffic, pavement and heat simultaneously.
Texas, by comparison, recorded 436,026 vehicle miles traveled per lane-mile, meaning its high overall score is more strongly influenced by extreme summer temperatures than unusually heavy roadway utilization.
Heat Can Put Additional Strain on Batteries, Tires and Cooling Systems
Extreme heat can affect vehicles as well as the roads beneath them.
AAA received more than 27 million emergency roadside assistance calls in 2024. Around 13 million involved towing, while roughly 7 million involved battery problems. Together, those two categories accounted for approximately 74% of roadside calls.
Battery degradation, cooling-system strain and tire deterioration can all become more pronounced during prolonged periods of high temperatures.
Tires are particularly significant because sustained heat can contribute to deterioration, blowouts and tread separation.
In 2024, the National Highway Traffic Safety Administration recorded 511 deaths in tire-related crashes. Those deaths were not classified as heat-caused, but federal transportation guidance warns that high temperatures can accelerate tire deterioration.
Vehicle efficiency can also decline.
AAA testing found that operating vehicles at 95°F reduced battery-electric vehicle efficiency by 10.4% and driving range by 8.5%, compared with testing at 75°F. Hybrid fuel economy fell by 12%.
Extreme Heat Is Associated With More Severe Crash Risk
The relationship between temperature and crash danger extends beyond vehicle maintenance.
A 2026 study covering more than 1.4 million crashes across 177 California cities found that at the 99th percentile of temperature, the relative risk of a severe crash increased to 1.35, while the relative risk of a fatal crash increased to 1.22.
Researchers also found elevated risks involving pedestrians and cyclists and a stronger heat-risk gradient at intersections.
The findings indicate an association between extreme temperatures and crash severity, but they do not establish that heat directly caused any individual collision.
A separate U.S. study cited by Attorney Brian White found a 3.4% increase in fatal crashes on heat-wave days compared with comparable non-heat-wave days.
Breakdowns Can Quickly Become Roadside Emergencies
Mechanical trouble is not necessarily dangerous on its own. The location where a vehicle becomes disabled can make the situation far more serious.
AAA Foundation research found that more than 2,100 people were killed outside disabled vehicles along roadsides between 2019 and 2023. These deaths were not heat-specific, but they demonstrate the potential consequences when a breakdown forces motorists or passengers to leave a vehicle next to active traffic.
Extreme road-surface temperatures can pose an additional danger.
Between June and August 2023, Arizona’s Valleywise Health burn center treated 136 patients for serious pavement-contact burns.
Among those patients:
- 14 died
- 34% required intensive care
- Many required skin grafts or multiple surgeries
The cases show how hot pavement itself can become a serious injury hazard during periods of extreme temperatures.
The Highest-Risk States Experience Far More Sustained Heat
The difference between states at the top and bottom of the ranking is substantial.
The 10 highest-ranked states averaged 63.8 statewide days reaching at least 90°F, compared with only 4.5 days among the bottom 10.
They also averaged 443,614 vehicle miles traveled per lane-mile, more than twice the 197,252 average among the 10 lowest-ranked states.
That combination increases the likelihood that high temperatures will overlap with heavily used roads and infrastructure already vulnerable to deterioration.
Heat Is Also Increasing Transportation Costs
The financial effects of extreme heat can reach drivers and public transportation agencies alike.
AAA testing found that operating vehicles at 95°F added approximately:
- $6.78 per 1,000 miles for an electric vehicle charged at home
- $16.25 per 1,000 miles when using commercial EV charging
- $13.02 per 1,000 miles for a hybrid vehicle
Separately, AAA’s 2025 driving-cost analysis estimated maintenance, repairs and tires for a new vehicle at 11.04 cents per mile, or roughly $8,280 over five years and 75,000 miles, before any additional heat-related repair costs are considered.
Crashes carry substantially larger costs.
The National Safety Council estimated the 2024 economic cost of a property-damage-only crash at approximately $6,600 per damaged vehicle, while a disabling injury was estimated at about $174,000 and a motor-vehicle death at roughly $2.05 million. These figures represent overall crash costs rather than heat-specific losses.
Public infrastructure could also become increasingly expensive to maintain. One national pavement study projected that rising temperatures could add approximately $19 billion in U.S. pavement costs by 2040 under a moderate warming scenario, rising to $26.3 billion under a higher-warming scenario.
How the Heat-Related Driving Risk Index Was Calculated
Attorney Brian White ranked the contiguous 48 states using six measures drawn from 2025 NOAA climate data and 2024 Federal Highway Administration road data.
| Measure | Weight |
|---|---|
| Average summer maximum temperature | 20% |
| Days at or above 90°F | 20% |
| Days at or above 100°F | 15% |
| Longest continuous 90°F-plus period | 15% |
| Vehicle miles traveled per lane-mile | 15% |
| Poor pavement share | 15% |
Alaska and Hawaii were excluded because equivalent finalized statewide NOAA data were unavailable for the climate measures used in the ranking.
The index measures relative road exposure and vulnerability rather than the probability that an individual driver will crash or experience a breakdown.
Taken together, Attorney Brian White’s analysis shows that the greatest heat-related transportation risks emerge where sustained extreme temperatures overlap with vulnerable pavement and heavily used roads.
Arizona stands out for the intensity and persistence of its summer heat, while Louisiana’s weaker pavement conditions push it above Texas despite Texas recording hotter temperatures. California presents another significant overlap between heat and poor roads.
As extreme temperatures become more persistent, the findings suggest the impact on American transportation could increasingly extend from damaged pavement and roadside breakdowns to higher operating costs, emergency repairs and more dangerous conditions for motorists.
