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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- Set your push alert preferences.
- Charge your phones and tablets so that if you lose power you can still watch live weather coverage in the App.