If you’re planning on traveling across Houston’s major roads during the winter storm this weekend, you’re going to want to be especially cautious driving on the city’s many bridges and overpasses.
THE LATEST: Winter Storm Watch issued ahead of Saturday’s possible freeze
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Here’s why:
Bridges have cold air on all sides
Regular roads are on the ground, which holds heat on its surface. The soil under normal roads acts like a thermal blanket, and slowly releases heat upward, allowing roadways to freeze slightly slower.
Bridges and overpasses are exposed to cold air above and below, so heat escapes much faster.
Faster icing, even with temperatures above freezing
Because bridges and overpasses get cold quicker and retain those low temperatures, they can freeze even when the air temperature is slightly above 32°F.
Moisture from rain, drizzle, or humidity can also play a factor turn into hazardous black ice much faster.
The Houston factor: Humidity
Houston’s high humidity means that moisture condenses and freezes easily.
This is why freezing temperatures in Houston can often feel much more drastic than they do in dryer, landlocked areas up north.
Why TxDOT warns drivers
This is why you often see:
“Bridges and overpasses may ice in cold weather”
Even if nearby roads seem fine, bridges can already be slick.