What Is the Urban Heat Island Effect and How Did It Impact Our Temperatures

In Dallas, the low was 73 degrees, while in Bowie it was 59 degrees. That is a 14 degree difference over 90 miles.

Lows in North Texas were below average for this time of year, making for a refreshing start to Wednesday morning! The official low at DFW Airport was 71 degrees. The normal low is 76 degrees. This is not the first time this summer North Texas had a morning this nice -- on June 26 and June 30, the low was 70 degrees at DFW Airport.

If you look at the low temperature map from Wednesday morning, you'll notice a big range in temperatures. In Dallas, the low was 73 degrees, while in Bowie it was 59 degrees. That is a 14 degree difference over 90 miles.


The reason for the steep temperature gradient is the Urban Heat Island Effect.

The difference in temperature between urban and rural areas has to do with how well the surfaces in each environment absorb and hold heat.

In rural areas, most of the region is covered with plants, grass, trees and farmland.

Plants take up water from the ground through their roots. Then, they store the water in their stems and leaves. The water eventually travels to small holes on the underside of leaves, the liquid water turns into water vapor and is released into the air. This cools the air. The process is called transpiration.

The opposite occurs in rural areas. In a major city like Dallas, materials such as asphalt, steel, concrete and brick cover the city. They are mostly dark colors — black, brown and grey. A dark object absorbs all wavelengths of light energy and converts them into heat, so the objects warm up. The buildings, sidewalks and construction equipment absorbed heat from the sun. Cities are typically hotter during the day and warmer at night.

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Before the Storm
Weather Safety
Stay Safe During a Hail Storm
At Home?
  • Head indoors immediately
  • If time allows, close all drapes, blinds or shades to prevent broken glass from entering your home.
  • Stay away from windows and skylights (any exterior glass) and head to a safe location inside your home, ideally only with interior walls.
  • Cover your head and seek shelter indoors immediately.
  • If you are trapped outside, get to a low-lying area and try to protect your head. Use clothing if it's all you have.
  • Stay inside your vehicle.
  • Slow down or pull over and stop at a safe location. DO NOT stop under a highway overpass. You may be protecting your vehicle, but you could be forcing other people to stop behind you.
  • Turn your back to windows or cover yourself with a blanket, coat or spare clothing to protect yourself from breaking glass.
  • If you have a sunroof, try to find something to protect your head.


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