Why is it hotter in cities in the summer?

Summers are hot and cities make that heat even worse. This is due to a phenomenon called an urban heat island.

It can be easily seen in Austin by comparing temperatures at Camp Mabry with temperatures at Austin-Bergstrom International Airport. On average daily high temperatures will be about 1-5° warmer at Camp Mabry than at ABIA. At night that differential gets even more significant with low temperatures between 2-8° warmer at Camp Mabry.  

The average high and low temperatures illustrate this difference very well. Camp Mabry’s average high temperature in June was 93° and low was 74°. Compare that to ABIA’s averages of 90° and 70°. Camp Mabry’s temperatures are averaging about 3.5° warmer overall when compared to Austin-Bergstrom.

What’s causing the difference? The things surrounding both airports. Camp Mabry is pretty much entirely surrounded by city. All the buildings make lots of heat, along with cars, roads, parking lots and fewer trees not to mention air conditioners make downtown Austin a relatively steamy place to be. Compare that with ABIA which is a big field surrounded by grass and a few comparatively small areas of pavement.

Heat from the sun is absorbed by buildings and re-emitted back into the atmosphere throughout the day and especially at night. The pavement on roads and parking lots do the same. All that combines to higher temperatures in the afternoon, and significantly higher temperatures overnight.  

Paved areas are especially egregious contributors to the urban heat island since they both emit much more heat than they absorb, they take up space that would otherwise be used by heat trapping things and they are impervious surfaces that forces water to run off rather than get absorbed. Fields, forests and general wild land all absorb more heat than they emit and trap and absorb more water when it rains. That rain then is evaporated by the sun which cools temperatures

That’s all well and good, but what impacts does that actually have on daily life? Well according to Climate Central the urban heat island amplifies air pollution by making oxides of nitrogen and ozone easier to form in the atmosphere. It also decreases the quality of life for those living in poorer areas that tend to have more paved spaces and fewer trees and fields.

Track your local forecast for the Austin area quickly with the free FOX 7 WAPP. The design gives you radar, hourly, and 7-day weather information just by scrolling. Our weather alerts will warn you early and help you stay safe during storms.
SUBSCRIBE: FOX 7 Austin Daily Newsletter | FOX 7 Austin on YouTube
FOLLOW: Facebook | Instagram | Twitter