Sunstroke? Why salt is currently being spread while it’s 36 degrees

July 1, 2025

Spreading in summer

It may sound contradictory: why on earth spread salt when it’s tropically warm? Today temperatures are running as high as 36 degrees, so the chances of slipperiness seem slim. Still, there is a layer of salt on traffic circles and intersections in some counties.

Soft asphalt

It has a logical explanation: at temperatures well above 30 degrees, asphalt can soften. Especially in places where many heavy vehicles accelerate, brake and steer, such as traffic circles, there is then a risk of rutting and deformation. The result: a bumpy road surface that can be dangerous for cars and motorcycles, as well as costly to repair once it cools down again.

How does salt work against heat?

The principle is actually quite simple. The salt on the asphalt attracts moisture from the air and allows it to condense on the road surface. The resulting thin layer of water cools the asphalt. This helps keep the road surface more stable at certain points and reduce damage. A smart emergency measure on extremely hot days, in other words.

How often does this happen?

In winter, gritting is a normal phenomenon, but gritting against heat is quite rare. It occurs only during extreme heat waves, when asphalt temperatures can rise toward or above 50 degrees. Such temperatures cause bitumen, the binder in asphalt, to soften. Early cooling with salt can prevent serious damage and costly repairs.

Important difference from winter spreading

Salt can sometimes cause slipperiness itself, as vehicles lose grip on salt residue. But unlike the thick layer of road salt in snow and sleet, heat control involves a thin layer that quickly dissolves or evaporates as soon as humidity and temperature change. Moreover, gritting focuses only on traffic circles and small sections where ruts are most likely to form. So you don’t have to go straight to the carwash today after a long drive.