DeKalb County could break a December weather record held since 1971 on Wednesday

DeKALB - If temperatures reach the 60s as expected Wednesday in DeKalb County, that would break a warm weather record for Dec. 15 the area hasn’t seen since 1971, according to the National Weather Service.

“It’s unusual to have this type of warmth in December, but it is not unheard of,” said Casey Sullivan, a meteorologist with the National Weather Service in Chicago. “It can happen, but it does not happen often.”

DeKalb County has a chance to break record-high temperatures twice this week. According to Wednesday’s forecast, there’s a 20% chance of showers in the afternoon with cloudy skies and a high near 67 degrees Fahrenheit, with a south wind blowing 15 to 25 mph. Thursday could see sunshine, and a high near 42 degrees with a breezy west wind 15 to 20 mph.

If temperatures reach the 60s Wednesday as expected, that will break a Dec. 15 record held in DeKalb County since 1971, according to the National Weather Service. The Dec. 15 record is 59 degrees in 1971.

Warmer weather was recorded on other days in December, however.

The warmest December day on record was 69 degrees on Dec. 4, 2012, according to the National Weather Service. The coldest day on record was minus 22 on Dec. 24, 1983. The overall lowest temperature for Sycamore and DeKalb recorded by the National Weather Service is minus 27 degrees Jan. 20, 1985.

“Based on our forecast, we are expecting to break the record high, both on the 15th and the 16th, again with the idea on the 16th that it will happen in the early morning hours when most people are sleeping,” Sullivan said.

According to the National Weather Service, the normal temperature range for Dec. 15 in DeKalb County is 19 to 34 degrees. The record minimum was minus 8 degrees in 1985. The normal temperature range for Dec. 16 is 19 to 33 degrees. The maximum record temperature was 58 degrees in 1984 and record minimum minus 5 degrees in 2016.

The National Weather Service Chicago office located in Romeoville doesn’t focus on any large scale weather research such as climate change trends.

“Thursday the 16th the temperature at midnight is going to be ahead of a cold front, you’ll see it in the lower 60′s just after midnight which will technically be the high for the day from a 24 hour calendar day perspective,” Sullivan said, “Temperatures will be falling as the cold front comes through. When everyone is up and awake on Thursday it’s not going to be 60 degrees.”

Sullivan noted a possible reason for the unseasonable weather is a low pressure system.

“It is just a very dynamic system, a very strong low pressure system that will be moving across the plains,” Sullivan said. “The Gulf of Mexico is wide open on the east side streaming warm moist air from the gulf up into our area. The warm air is really just a function of how much moisture is being pushed into the area from the gulf.”