Extreme summer heat is creating a new set of risks for American drivers, and some states face a much more dangerous combination of high temperatures, deteriorating pavement and heavily traveled roads than others.
A nationwide study from Attorney Brian White ranks Arizona as the state with the greatest heat-related driving risk in the continental United States, giving it a score of 88.83 out of 100. Louisiana follows at 80.69, while Texas ranks third at 79.68.
The Heat-Related Driving Risk Index examined more than temperature alone. Researchers combined average summer maximum temperatures, the frequency of days reaching 90°F and 100°F, the longest uninterrupted stretch of 90°F weather, traffic exposure and the share of roads already classified as being in poor condition.
That combination matters because heat does not affect every road system the same way. A state can experience extremely high temperatures but have relatively strong pavement or less concentrated traffic. Another state may be slightly cooler but have substantially more vehicles using roads that are already vulnerable to deterioration.
The findings suggest that the greatest risks emerge where those conditions overlap.
Arizona Leads the Nation for Heat-Related Road Risk
Arizona’s No. 1 position is driven by some of the most extreme summer temperature conditions in the country.
The state recorded an average summer maximum temperature of 95.79°F, the highest among the states included in the study. Arizona also averaged 80 days at or above 90°F, more than any other state, and recorded 21 statewide days reaching at least 100°F. It was the only state with a double-digit total for that most extreme temperature category.
Texas was not far behind on the temperature measures. Its average summer maximum reached 93.45°F, second nationally, while the state recorded 78 days at or above 90°F.
Texas and Mississippi also shared the longest uninterrupted stretch of extreme summer heat in the analysis, with 43 consecutive days at or above 90°F.
| State | Heat-Risk Finding |
|---|---|
| Arizona | No. 1 overall, 88.83 risk score |
| Louisiana | No. 2 overall, 80.69 |
| Texas | No. 3 overall, 79.68 |
| Arizona | Highest average summer maximum, 95.79°F |
| Texas | Second-highest average summer maximum, 93.45°F |
| Arizona | 80 days at or above 90°F |
| Texas | 78 days at or above 90°F |
| Arizona | 21 days at or above 100°F |
| Texas and Mississippi | 43-day continuous 90°F-plus stretch |
Louisiana’s second-place ranking demonstrates why the index does not simply rank states by temperature.
Although Texas experienced hotter conditions, Louisiana had substantially more pavement rated in poor condition. About 16.1% of Louisiana’s measured arterial mileage met the study’s definition of poor pavement, compared with 7.3% in Texas. That additional infrastructure vulnerability helped push Louisiana above Texas in the overall ranking.
Florida also ranked among the five highest-risk states. Its average summer maximum reached 92.07°F, accompanied by 76 days at or above 90°F and a continuous 35-day period of 90°F-plus temperatures.
At the opposite end of the index, North Dakota recorded the lowest risk score at 13.56, followed by Minnesota at 13.67 and Wyoming at 18.56.
Poor Roads Can Magnify the Effects of Extreme Heat
Heat is particularly challenging for pavement that has already deteriorated.
Road materials expand as temperatures rise. Existing weaknesses caused by age, moisture, heavy traffic or previous damage can make road surfaces more susceptible to rutting, cracking, deformation or buckling when prolonged heat adds additional stress.
Attorney Brian White’s study found that Rhode Island had the largest share of poor pavement at 31.3%, followed by California at 27% and Massachusetts at 24.5%.
| State | Poor Pavement Share |
|---|---|
| Rhode Island | 31.3% |
| California | 27.0% |
| Massachusetts | 24.5% |
| New Jersey | 18.5% |
| New Mexico | 18.2% |
| Louisiana | 16.1% |
| Texas | 7.3% |
Rhode Island’s position is another example of why one factor cannot explain the overall heat-risk ranking. Despite having the nation’s largest poor-pavement share, Rhode Island ranked only 29th overall because its exposure to extreme summer heat is substantially lower.
California presents a more concerning combination. It was among the five states with the highest overall heat-related road risk while also recording the second-largest share of poor pavement.
Research cited in the study also shows how rapidly pavement performance can change as surface temperatures rise. In one modeling analysis, rut depth increased from approximately 4 millimeters at a pavement temperature of 34°C to 8 millimeters at 49°C. At 63°C, modeled rutting reached about 13 millimeters.
Houston Has Already Seen Roads Buckle During Extreme Heat
Texas provides a real-world example of how those conditions can affect active roadways.
During a roughly two-week period of intense heat, the Texas Department of Transportation reported damage on at least 10 Houston-area roads, including an entrance ramp to Interstate 10 and Highway 6 near Alvin. Highway 146 in Baytown also required emergency overnight repairs.
TxDOT linked the damage to a combination of extreme temperatures, prolonged sunshine and recent rainfall.
The issue extends beyond individual Houston-area incidents.
Attorney Brian White’s analysis reports that TxDOT identified 788 roadway miles in its Laredo District as highly vulnerable to extreme heat, accounting for more than half of the state’s roadway mileage classified at that level of vulnerability.
Potential consequences identified by transportation officials include:
- Pavement rutting
- Buckling
- Cracking
- Temporary road closures
- Detours
- Traffic disruptions
- Accelerated deterioration
These problems can create immediate hazards for motorists while also increasing maintenance demands on state transportation systems.
Traffic Exposure Creates Another Layer of Risk
A damaged or overheated road becomes more consequential when large numbers of vehicles are using it.
Attorney Brian White measured traffic exposure using vehicle miles traveled per lane-mile, which helps show how intensively a state’s available road network is being used.
New Jersey had the greatest traffic exposure in the study at 937,163 vehicle miles traveled per lane-mile, followed by Florida at 891,656, California at 821,885, Maryland at 795,063 and Massachusetts at 794,675.
| State | Vehicle Miles Traveled per Lane-Mile |
|---|---|
| New Jersey | 937,163 |
| Florida | 891,656 |
| California | 821,885 |
| Maryland | 795,063 |
| Massachusetts | 794,675 |
| Texas | 436,026 |
Yet New Jersey ranks only 18th overall.
Texas, meanwhile, has a much lower VMT-per-lane-mile figure of 436,026 but still ranks third because its sustained heat exposure is so extreme.
The contrast illustrates the logic behind the index: heat, pavement and traffic are separate risks that can reinforce one another when they occur in the same place.
Heat Can Also Turn Vehicle Problems Into Roadside Emergencies
The road itself is only one part of the problem.
High temperatures can accelerate battery degradation, strain vehicle cooling systems and place additional stress on tires. AAA reported receiving more than 27 million emergency roadside calls during 2024, with roughly 13 million requiring towing and about 7 million involving battery problems. Those two categories accounted for approximately 74% of AAA’s roadside calls.
Not every breakdown is caused by heat, but prolonged high temperatures can increase stress on several vehicle systems.
Tires represent another significant safety concern. The National Highway Traffic Safety Administration reported 511 traffic fatalities in tire-related crashes during 2024. NHTSA also warns that insufficient maintenance can contribute to flat tires, blowouts and tread separation.
For a driver traveling through extreme heat, a mechanical failure can create two risks at once: the initial problem with the vehicle and the danger of being stranded beside moving traffic.
AAA Foundation research found that more than 2,100 people were killed outside disabled vehicles along roadsides between 2019 and 2023. Those deaths were not classified as heat-related, but they demonstrate how a breakdown can place drivers and passengers in a dangerous roadside environment.
Research Links Extreme Temperatures With More Severe Crashes
Temperature may also affect crash outcomes.
A 2026 analysis cited by Attorney Brian White examined more than 1.4 million crashes across 177 California cities and found higher relative risks for severe and fatal crashes during extreme temperatures.
At the 99th percentile of temperature exposure, the relative risk reached 1.35 for severe crashes and 1.22 for fatal crashes. Pedestrian- and bicycle-involved crashes showed particularly elevated risk, while intersections displayed a stronger heat-risk gradient than other road environments.
Those findings establish an association rather than proving that heat directly caused any individual crash.
A separate U.S. analysis cited in the study found a 3.4% increase in fatal traffic crashes on heat-wave days compared with comparable non-heat-wave days.
Heat-Related Road Risk Can Carry a Major Economic Cost
Extreme heat can also increase the financial burden of transportation.
Attorney Brian White found that states in the top 10 of the Heat-Related Driving Risk Index averaged 63.8 days at or above 90°F, compared with just 4.5 days among the bottom 10.
The top 10 also averaged 443,614 vehicle miles traveled per lane-mile, more than twice the 197,252 average among the bottom 10.
Crash costs can escalate quickly once a roadway or vehicle problem results in a collision.
The National Safety Council estimates the average 2024 economic cost at:
| Crash Outcome | Estimated Economic Cost |
|---|---|
| Property-damage-only crash | $6,600 per damaged vehicle |
| Disabling injury | $174,000 |
| Motor-vehicle death | $2.05 million |
These are national economic estimates and are not specific to heat-related crashes.
Public agencies may also face growing infrastructure costs. Research included in the Attorney Brian White study projected that increasing temperatures could add approximately $19 billion to U.S. pavement costs by 2040 under a moderate warming scenario, rising to $26.3 billion under a higher warming scenario.
How Attorney Brian White Ranked America’s Hottest Roads
The Heat-Related Driving Risk Index ranks the contiguous 48 states using six measures.
| Index Component | 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% |
Climate measures were based on June through August 2025 data, while road metrics came from 2024 federal highway statistics. Each measure was converted into a state-relative score and weighted to create the final index. Alaska and Hawaii were excluded because equivalent finalized statewide climate data were unavailable for the measures used.
The scores do not represent a driver’s probability of crashing. Instead, they compare how strongly extreme heat, road use and infrastructure vulnerability overlap from one state to another.
That distinction helps explain why Arizona, Louisiana and Texas emerge as the country’s three highest-risk states for heat-related driving, but for different reasons. Arizona experiences the most intense sustained heat. Louisiana combines high temperatures with poorer pavement. Texas pairs persistent extreme heat with increasingly visible stress on roads in places such as Houston.
The broader finding from Attorney Brian White’s analysis is that high temperatures are no longer just a comfort issue for motorists. As heat interacts with pavement, tires, batteries, traffic and roadside exposure, summer weather can create a chain of risks that follows drivers from the road surface beneath their vehicles to the machinery keeping those vehicles moving.
