In High Valley Temperatures, Some Surfaces Are Hotter Than Others

July 23, 2014

As the next few days bring near-record heat to the Valley, most residents know to drink water and stay inside when possible. But if you have to be outside, be aware of the surfaces you surround yourself with.

Valley temperatures are continuing to rise with Wednesday’s high near 114 degrees and overnight low of 95 degrees, one degree cooler than the record set in 2003. If you are outside either day or night, ambient heat varies depending on the density of the material around you. 

According to Nancy Selover, ASU Climatologist, less dense surfaces are the hottest during the day.

"The bare dirt is really what gets you because the solar radiation is absorbed at the surface," Selover said. "And when you have a lot of porous spaces, air spaces between particles, like you have in dirt, then the heat is not conducted down deep into the dirt. It all stays very near the top."

At night, bare dirt releases heat quicker becoming cooler compared to more dense material such as pavement and concrete. Those surfaces release heat slower creating higher overnight temperatures.

Selover notes increased installation of porous concrete and pavement will help release heat quicker and allow for rainwater to access ground soil, helping to keep ambient temperatures even cooler at night.