Precisely! The wind blowing over and under the bridge caused a wind chill and can freeze water on the bridge surface when the actual air temp is > 32.

I'd bet if the wind is high enough, and the bridge long enough, it might drop a degree or 2.

Several years back in an E39 M5, I ran into a hail storm in May on a road out in the country. It lasted 10-15 minutes and there was no where I could go. The road became covered with hail marbles, was slick as heck, and the temp display dropped from 70 to 35!!! I got the ding. I finally managed to find an awning and pulled off the road under cover. The lot was so slick, I could barely make it back on the road after it passed. The end result was a $2000 Dent Wizard bill.
NationWide processed several 1000 claims that day!

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Richard
Sir Snaps-a-lot, 9 Time Dragon Slayer (54 runs!)
2011 X5 50i Alpine White, Biege Nappa /Lt Poplar M Sport
2009 Z4 35i, Black Sapphire/Ivory-Black/Anthracite

Gone but not forgotten: '08 550i, '06 X3, '06 650i, '02 M5, '99 540i