The temperature plunged to minus 27 at the Whiteside County Airport in Rock Falls early Monday. Even the weatherman admits that was unexpected.
“You had the coldest air in the Midwest,” said Andy Ervin, a meteorologist for the National Weather Service in the Quad Cities. “It was pretty remarkable. No other place was close to what you saw in Rock Falls and Sterling.”
The temperature hit its low about 7:30 a.m.
Towns such as Mount Carroll, Princeton and DeKalb saw temperatures nowhere near that low.
Why the difference?
Unlike the others nearby towns, Sterling and Rock Falls are in the Rock River Valley, and a combination of circumstances, including calm winds and fresh snow cover, allowed temperatures to plummet, said Mike McClure, a meteorologist with the National Weather Service in the Quad Cities.
“It was just the perfect setup,” he said. “The dense, cold air settled in the river valleys, and you had no wind to scour out that cold air.”
The phenomenon applied to other areas. For instance, Rockford, which the Rock River cuts through, saw a temperature of minus 16 shortly after 7:30 a.m., while the temperature was minus 12 in Freeport to the west and minus 8 in Marengo to the east.
By noon, the temperature in Sterling and Rock Falls had risen to 7 degrees, similar to other towns in the area.
The cold temperatures are expected to continue, with a high of 26 degrees today and 15 degrees on Wednesday.
Today – High of 26 degrees; 4 to 8 inches of snow
Wednesday – High of 15, but low plummets to minus 13
Thursday – Colder, on the whole; high of 6, low of minus 4