Fifteen volunteers drove around King County and Seattle on Monday tracking the weather, as temperatures rose above 90 throughout the area.
The volunteers used a probe to figure out which areas suffer the most in hot weather.
"They will be driving around specific routes to kind of catch the difference. There can be up to a 20-degree difference between city blocks," said Jamie Stroble with the King County Climate Action Team.
The volunteers recorded temperatures in 15 geographic areas at three different times of the day.
All of the information collected during the one-day study will help researchers create a heat map of the area.
"We know that people with existing health disparities and chronic health issues like heart disease, diabetes, are more at risk of health impacts when we get these hot temperatures, people over age 65, pregnant women, children, people taking certain medications," said Lara Whitely Binder, Climate Preparedness Specialist for King County.
The study gives both King County and the city of Seattle a chance to look into some of the obstacles that may prevent areas from cooling down at night and then work to fix those issues.
"It can range from trying to increase the tree canopy in an area so that you get more shading. We can try to increase access to green space, again, with trees so people have a place when it's hot to go take refuge and enjoy some outside time in shade," said Whitley Binder.
County leaders say mapping heat trends is critical work that will help the area as a whole prepare for more hot days as the climate continues to change.
"This is not something that's going to go away. This is a problem that's only going to get worse in time," said Whitley Binder.
Other cities are conducting similar studies across the country.
Tacoma launched a similar study last year.