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Ask Andrew: Do colder winds push more on a truck and trailer?

A News 8 viewer asks if the temperature of the air impacts how much the wind pushes on a vehicle.

MOLINE, Ill. — We've had our fair share of wind lately here in the Quad Cities. That led avid News 8 viewer Loren Bird from Ladd, Illinois, to ask: Do cold winds push harder on a truck and trailer? More specifically, a semi-truck? 

Let's dig in!

First, we need to get through a mini chemistry lesson. One of the dirty little secrets in meteorology deals with air density. It's easy to see why some would assume that warmer air would be denser, especially here in the Midwest as oftentimes that warmth is also accompanied by added moisture. You'd think all that added water vapor would indeed make the air more dense, right? 

Surprisingly, wrong! Increasing the water vapor in a mass of air actually makes it lighter. Remember what water is made up of, hydrogen and oxygen. Hydrogen, being the first element on the periodic table of elements, is the lightest element of them all. If you have more water (H20) then you squeeze out more of the heavier air molecules, making the air mass less dense. 

Still with me? I know, it's confusing. 

Credit: WQAD

In summary, cold air is denser because molecules are moving slowly and more tightly packed together. They occupy more space. Warmer air, however, features molecules that are farther apart from each other, moving much more slowly and occupying less space. 

With this new knowledge, it's easy to see why a strong cold wind would have more push on a truck, especially a semi-truck. You've got far more air molecules running into the truck itself compared to if that wind was a warmer wind. 

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