Last month was the warmest and second-wettest December in Illinois history according to state Climatologist Jim Angel.
“The statewide average temperature for December was 40.6 degrees, an incredible 10.7 degrees above average and the warmest December on record,” Angel said Monday. “This December beat the old record by 1.7 degrees that was set in 1923 with 38.9 degrees.”
The statewide average precipitation was 6.7 inches, just over 4 inches more than the average rainfall in Illinois for the month of December, 2.67 inches.
“The (previously) wettest December on record was in 1982 with 7.17 inches,” Angel said. “Like this year, that was also during a major El Niño event.”
With the wet finish, 2015 became the sixth-wettest year in Illinois history with 48.49 inches of precipitation. That’s 8.53 inches above the average of 39.84 inches.
The average temperature would have been significantly higher if not for an extremely cold February, Angel said. The average was 52.8 for 2015, .4 degrees above average.
January is off to a much cooler start. But it is expected to be dry — at least until the middle of the week.
Skies will be cloudy early Monday, according to the National Weather Service. The clouds will break up as the day goes on. But the sun won’t warm things up much as the high temperature reaches only 35.
That’s three degrees cooler than the average high temperature for early January in the St. Louis metropolitan area, 38.
Angel said the warm and wet December is no guarantee things will stay that way.
“We’ve sort of shifted gears and now we’re into a pattern of closer to normal temperatures and precipitation,” Angel said.
It will be partly cloudy Monday night with a low of 22.
Skies will be mostly sunny Tuesday with a high of 40. Tuesday night, the low will be 26 under partly cloudy skies.
It will be partly sunny Wednesday with a high of 44.
The possibility of rain returns to the forecast Wednesday night with a 20 percent chance of showers and a low of 33.
There is a 50 percent chance of rain Thursday, a 60 percent chance Thursday night and a 40 percent chance Friday.
The rain isn’t expected to have much of an impact on receding flood waters.
After reaching a high of 42.58 feet Saturday at the St. Louis riverfront, the Mississippi dropped below major flood stage, 40 feet, Sunday and is expected to reach 34.6 feet Monday. That is half a foot below the threshold for moderate flood stage.
The forecast calls for the river to be back within the normal range, below 28 feet, by Friday.