Here’s what the urban heat island effect does on a 100° day

August 18, 2022 5:05 PM

Matt Gray,

Posted: August 18, 2022 5:05 PM

Updated: August 18, 2022 7:28 PM

by Matt Gray

SPOKANE, Wash.– As the land from Spokane to Coeur d’Alene becomes more of a concrete jungle, the chances for extremely hot weather rise with the development. Roads, parking lots, and sidewalks absorb more heat from the sun than a grassy field or a shady forest. This creates what’s called the urban heat island effect.

Since 4 News Now started to report temperatures from downtown Spokane this month, the extra heat has stuck out like a sore thumb. The weather station we use for downtown temperatures is the Perry Curves WSDOT station on the edge of downtown and East Spokane.

On Wednesday for example, the official Spokane climate station at the airport hit the upper 90s. The downtown weather station hit 100°. Thursday has been a similar pattern. While the airport temperature might be a good approximation for temperatures on the north side or the south hill, the downtown corridor appears to be one of the hottest places in Spokane or Kootenai counties during the dog days of summer.

The reason why is simple, the more urban development you have, the hotter temperatures you’re likely to get. The fact that downtown is at the bottom of a valley can also capture heat from the hillsides, which will crank up the temperature too. Early Thursday afternoon, pavement temperatures in the KXLY parking lot downtown were reaching 140°! A patch of grass next to our lot was hovering at just 104°. There’s no doubt that on a micro-level that temperature difference translates to the air above these surfaces.

Another revealing test in our lot proves that shade is one of the best ways to keep cool. Even on our blacktop parking lot, that 140° pavement in the sun was under 90° in the shade!

Gonzaga University is studying urban heat in Spokane this summer and hopes to make a map showing the hottest neighborhoods in the city. With that knowledge, city leaders can take steps to cool off some of these urban heat islands so that summer heat can be more bearable in the future.