Extreme heat does more than make summer driving uncomfortable.

High temperatures can accelerate tire wear, weaken vehicle batteries, strain cooling systems, damage pavement and leave motorists exposed to dangerous conditions when vehicles break down. Emerging research also suggests that the most extreme temperatures are associated with an increased risk of severe and fatal crashes.

Those risks are not distributed evenly across the United States.

A state-by-state analysis from Attorney Brian White found that Arizona faces the country’s highest combined heat-related driving risk, earning a score of 88.83 out of 100. Louisiana ranked second at 80.69 and Texas third at 79.68.

The ranking compares the contiguous 48 states across temperature, prolonged heat, road use and pavement quality, providing a broader picture of where extreme summer conditions place the greatest strain on drivers and transportation systems.

Arizona Records the Most Extreme Summer Conditions

Arizona’s No. 1 ranking is closely tied to the scale of its summer heat.

The state recorded the highest average summer maximum temperature in the country at 95.79°F.

It also experienced:

• 80 statewide days at or above 90°F
• 21 statewide days at or above 100°F
• The highest number of 90°F days included in the analysis
• The only double-digit statewide total of 100°F days

Those figures gave Arizona one of the most consistently extreme heat profiles in the country.

Texas was not far behind.

The state recorded an average summer maximum of 93.45°F, the second-highest result nationally, as well as 78 days at or above 90°F. Texas and Mississippi shared the longest continuous stretch of 90°F-plus conditions, at 43 consecutive days.

Louisiana’s second-place overall ranking demonstrates why temperature alone does not determine transportation risk. Its heat conditions were less severe than Texas’, but the state’s weaker pavement and other road-exposure factors pushed its combined score higher.

Damaged Pavement Can Turn Heat Into a Transportation Problem

High temperatures can cause pavement materials to expand and soften, particularly on roads already weakened by traffic, moisture or age.

Attorney Brian White’s analysis found substantial differences in pavement quality nationwide.

Rhode Island had the largest proportion of arterial pavement classified as poor, at 31.3%.

The five highest shares were:

State	Poor Pavement Share
Rhode Island	31.3%
California	27.0%
Massachusetts	24.5%
New Jersey	18.5%
New Mexico	18.2%

Rhode Island still ranked only 29th overall because its summer heat exposure was substantially lower than conditions in states such as Arizona, Louisiana and Texas.

California, however, represents one of the clearest overlaps between significant heat and already-poor pavement, appearing among the highest-ranking states in both categories.

Louisiana offers another example. 16.1% of its pavement was classified as poor, more than twice the 7.3% recorded in Texas. That difference helps explain why Louisiana ranks ahead of Texas despite having less extreme heat.

Laboratory and modeling research indicates that pavement deformation can rise sharply as temperatures increase. One 2025 pavement study cited in the analysis found modeled rut depth climbing from 4 millimeters at 34°C to 8 millimeters at 49°C, before reaching approximately 13 millimeters at 63°C.

Texas Has Already Seen Heat-Damaged Roads

The infrastructure risk is not merely theoretical.

During a recent period of extreme heat, the Texas Department of Transportation identified damage affecting at least 10 Houston-area roadways over roughly two weeks.

The incidents included an Interstate 10 entrance ramp, Highway 6 near Alvin and Highway 146 in Baytown, where a damaged section required overnight emergency repairs.

TxDOT has also identified 788 roadway miles in the Laredo District as highly vulnerable to extreme heat, accounting for more than half of Texas roadway mileage identified in that highest vulnerability category.

Potential consequences include pavement cracking, rutting and buckling, along with lane closures, detours and traffic disruptions.

Hot Weather Can Increase the Risk of Vehicle Failure

Road deterioration is only one part of the problem.

High temperatures also place stress on the vehicles traveling across those roads.

AAA responded to more than 27 million roadside assistance calls in 2024. Approximately 13 million required towing, while another 7 million involved battery trouble, meaning those two categories accounted for around 74% of all calls.

Although those incidents were not all caused by high temperatures, AAA identifies battery failure, engine problems and flat tires as common summer travel issues.

Heat can accelerate battery degradation, increase demand on vehicle cooling systems and place additional stress on tires.

The National Highway Traffic Safety Administration recorded 511 deaths in tire-related crashes in 2024. Those fatalities are not classified as heat-related, but NHTSA warns that sustained high temperatures can accelerate tire deterioration and increase the risk of problems such as tread separation or blowouts.

Vehicle Efficiency Falls at 95°F

Extreme temperatures can affect how efficiently vehicles operate even when they do not break down.

AAA testing comparing operation at 95°F with a 75°F baseline found that battery-electric vehicles experienced a 10.4% reduction in efficiency and an 8.5% reduction in driving range.

Hybrid vehicles experienced a 12% reduction in fuel economy under the same hotter conditions.

Those efficiency losses translate into higher operating costs.

At 95°F, AAA estimated an additional cost of approximately:

Vehicle/Charging Type	Added Cost per 1,000 Miles
Home-charged EV	$6.78
Commercially charged EV	$16.25
Hybrid vehicle	$13.02

The increases may appear modest on a per-trip basis, but repeated heat exposure can add costs over a full summer or several years of ownership.

Research Links Extreme Temperatures With More Severe Crashes

The most significant concern is whether extreme heat also contributes to more dangerous collisions.

A 2026 study analyzing more than 1.4 million crashes across 177 California cities found that crash severity increased during the most extreme temperatures.

At the 99th temperature percentile, researchers found:

• Relative risk of severe crashes: 1.35
• Relative risk of fatal crashes: 1.22

The study also found elevated risks for collisions involving pedestrians and cyclists and observed a steeper heat-related risk gradient at intersections.

These results demonstrate statistical associations rather than proving that temperature caused any individual crash.

A separate U.S. study cited by Attorney Brian White found that fatal traffic crashes increased by 3.4% on heat-wave days compared with similar non-heat-wave days.

Those findings suggest that the transportation consequences of extreme heat may extend beyond mechanical failures or damaged infrastructure.

A Breakdown Can Become a Fatal Roadside Event

A disabled vehicle can create an additional hazard if drivers or passengers are forced to stand close to moving traffic.

AAA Foundation research found that more than 2,100 people died outside disabled vehicles between 2019 and 2023.

The fatalities were not specifically linked to heat, but they demonstrate how mechanical failures can escalate into much more dangerous roadside situations.

That distinction is important when evaluating extreme heat. A dead battery or overheated engine may initially be a vehicle-maintenance problem, but a breakdown occurring on a busy highway can expose occupants to passing traffic.

Pavement Itself Can Become Dangerous

Some of the most extreme consequences of hot roads occur outside vehicles entirely.

Between June and August 2023, 136 patients were treated for severe pavement-contact burns at Arizona’s Valleywise Health burn center.

Of those patients:

• 14 died
• 34% required intensive care
• Many underwent skin grafts
• Some required multiple surgeries

The cases demonstrate the temperatures road surfaces can reach under extreme summer conditions and the severity of injuries possible when a person comes into prolonged contact with hot pavement.

Traffic Exposure Varies Sharply Across States

Attorney Brian White’s index also accounts for the amount of traffic moving across each state’s available road network.

Using vehicle miles traveled per lane-mile, New Jersey recorded the highest traffic exposure at 937,163.

It was followed by:

• Florida: 891,656
• California: 821,885
• Maryland: 795,063
• Massachusetts: 794,675

Despite ranking first on traffic exposure, New Jersey placed only 18th overall because its summer temperatures were less severe.

Texas recorded 436,026 vehicle miles traveled per lane-mile, indicating that its third-place overall score is driven more heavily by sustained high temperatures than by an unusually congested road network.

The Top Heat-Risk States Face Far More 90°F Days

The difference between the highest- and lowest-risk states becomes particularly clear when looking at the frequency of hot days.

The 10 highest-ranked states averaged 63.8 statewide days at or above 90°F.

The 10 lowest-ranked states averaged just 4.5.

Traffic exposure was also significantly higher in the top group, averaging 443,614 vehicle miles traveled per lane-mile, compared with 197,252 among the bottom 10.

That means the states facing the greatest risk generally combine much more persistent heat with substantially greater vehicle exposure.

Heat Could Add Billions to Road Maintenance Costs

Extreme temperatures can also create substantial financial consequences for public agencies.

A national pavement study cited in Attorney Brian White’s analysis projected that rising temperatures could add approximately $19 billion to U.S. pavement costs by 2040 under a moderate warming scenario.

Under a higher-warming scenario, the projected additional cost climbs to $26.3 billion.

The federal government has already established programs aimed at strengthening transportation infrastructure against climate and weather hazards. The PROTECT program provides $8.7 billion over five years for transportation resilience projects.

Drivers also face the broader financial burden associated with collisions.

National Safety Council estimates put the economic cost of a property-damage-only crash at approximately $6,600 per damaged vehicle, while a disabling injury costs around $174,000 and a motor-vehicle death approximately $2.05 million. Those are national estimates for crashes generally, not crashes specifically caused by heat.

How the States Were Ranked

Attorney Brian White’s Heat-Related Driving Risk Index uses six equally related but separately weighted measures.

Index Measure	Weight
Average summer maximum temperature	20%
Statewide days at or above 90°F	20%
Statewide days at or above 100°F	15%
Longest uninterrupted 90°F-plus period	15%
Vehicle miles traveled per lane-mile	15%
Poor pavement share	15%

The climate components use June through August 2025 NOAA data, while road measures draw from 2024 Federal Highway Administration statistics. Alaska and Hawaii were excluded because equivalent finalized statewide NOAA daily-grid data were unavailable for the relevant measures.

The score is a comparison of exposure and road vulnerability, not a measure of the probability that a particular motorist will crash, suffer a breakdown or encounter damaged pavement.

Still, the overall pattern is clear.

Arizona faces the greatest combination of persistent extreme heat and road exposure, while Louisiana and Texas follow because different combinations of high temperatures, traffic and pavement conditions compound their risks.

The broader data compiled by Attorney Brian White also show why heat is becoming a transportation issue rather than simply a weather issue. It can affect pavement, batteries, tires, fuel and energy efficiency, roadway maintenance and the safety of motorists who find themselves stranded next to active traffic.

As hotter conditions become more persistent, the effects could increasingly be measured not only in degrees Fahrenheit, but in road repairs, vehicle failures, higher operating costs and more dangerous conditions for drivers across the country.