Nearly all regions of the country have been experiencing hot, repressive temperatures this summer. As we have noted in the past, winter tires generally don’t stop as well as all-season and summer tires on dry and wet roads, and because they wear quicker, it just makes sense to remove them when spring arrives. But how do all-season tires fair with the change of seasons and temperature?

We’ve been studying the effects of road temperature on stopping distances and found that that drivers should expect shorter stops on cooler road surfaces. In one instance, our test car took 134 feet to stop from 60 mph on our dry track when the surface was 35ºF. Stopping distances when the track was at a blistering 119ºF, typical of summer-time road temperatures, took an extra nine feet. Nearly all the cars we’ve tested follow this trend; admittedly some are less affected by a hot road than others.

On a wet surface, stopping distances appear to be even more sensitive to temperature variation. We measured a truck taking 166 feet to stop from 60 mph on a 107ºF wetted surface, but on a cooler day (at 74ºF), the truck stopped 11 feet shorter.

Some consumers may conclude that roads become slicker when they get hot. That supposition might be partially true depending on the road’s construction, with oils permeating to the surface particularly after a rain storm, but industry studies show a tire’s peak friction on a surface declines as the road heats up. How much change depends on the road, tire, and your vehicle’s braking characteristics.

Bottom line: Leave more room between you and the car you are following in extremely hot weather. Also, be a vigilant driver encountering sudden thunderstorms that add many challenges to stopping in the summer. Tires generally take longer to stop on wet roads—especially if the road surface is hot—and longer still if oils and rubber debris are lifting off the wetted surface. Sudden down-pours of rain can result in water “ponding” on the road, which can lead to hydroplaning as tires start to skim on water causing a loss of vehicle control. So slow down in the hot summer, drive cautiously, and pay attention to the weather conditions.

Related:
Tips for keeping cool in hot summer cars
What to do if your car overheats