Friday, April 9, 2010

26 Degrees This Morning

The official low at the Chicago-Rockford International Airport was 26 this morning. That's two degrees below what I predicted, but nowhere near the lowest temperature in the contiguous 48 states. That "honor" belongs to Stanley, ID. They hit 4 degrees BELOW zero this morning. (When I see that number, I have to remind myself that it's April 9th and not February 9th!)

Stanley Idaho sits high in a northern Rocky Mountain valley at an elevation of 6,253' above sea level. That's a shade higher than Denver. The reasons Stanley gets so cold are its northerly latitude, elevation, and the fact that it sits in a valley. On clear, calm nights, cold air from the surrounding mountains drains into town. That's because cold air is more dense -- or "heavier" -- than warm air.

Although northern IL doesn't have mountains, we can also see temperatures drop in some of the low spots at night. Tonight will be an interesting night to watch for that. Winds are light and skies should remain mostly clear through daybreak. It'll be interesting to see if Rochelle -- which sits in a low, swampy area -- falls close to the freezing mark again... Even though temperatures in most spots will only drop into the mid and upper 30s.

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