January – Illinois State Climatologist

February 2, 2016

January – Wild Temperature Swings and Dry

Summary: January in Illinois finished out at 26.7 degrees, 0.3 degrees above average. Both precipitation and snowfall were below average. The statewide average precipitation (rain plus water content of snow) was 0.85 inches, 1.22 inches below average. Snowfall was below average across most of the state.

Temperature

The temperatures in January in Illinois showed some very large swings that tended to cancel each other out in the end since we finished 0.3 degrees above average. The first 9 days were above average, followed by 4 days below average, then 3 days above average. The second half of January started out much below average, but steadily warmed and by the end of the month was 20 degrees above average.

While the magnitude of the swings were impressive, the pattern of warm and cold stretches is typical of winter in Illinois and represents the passage of warm and cold fronts across the region. Because it may take a day or more for a system to pass through Illinois, the dates and size of the temperature departures at a particular station may not correspond to the statewide numbers, especially in far southern Illinois.

Precipitation

The January precipitation (left) and departures from average (right) show that precipitation was uniformly light across Illinois, just under an inch in most places (light green) and just over an inch below average (shades of yellow).

Snowfall

The January snowfall (left) ranged from 2 to 5 inches in most locations. Western Illinois saw 5 to 7.5 inches. However, as the panel on the right indicates most of Illinois received below-average snowfall (shades of beige and yellows).

February 2, 2015

January 2015 in Illinois – Cool and Dry

January 2015 in Illinois was cooler and drier than average. The statewide temperature was 25.4 degrees, 1 degree below average and the 53rd coldest on record. However, it was not nearly as cold as last January when the average temperature was 19.3 degrees and ranked as the 16th coldest on record.

The statewide average precipitation for January 2015 was 1.53 inches, 0.5 inches below average. Because of dry weather in November, December, and January, the US Drought Monitor introduced “D0” in northern and western Illinois. As I explained in an earlier post, this is not a great concern yet because of the low demand for water in winter but we are watching the situation.

Snowfall ranged from less than an inch in the far south to 10 to 15 inches north of Interstate 80 (first map). That results in above-average snowfall in the northern half of the state and below-average for the southern half (second map). However, this was far less snow than January 2014 (last map) when most of the state was covered with 10 to 25 inches of snow. Continue reading “January 2015 in Illinois – Cool and Dry”

December 18, 2014

Mild Winter Weather Not Expected to Last in Illinois

The mild winter weather is not expected to last in Illinois, but you probably already knew that.

How mild has December been? As of December 18, the statewide average temperature for December stands at 34.3 degrees, 2.1 degrees above average. Precipitation (both rain and the water content of snow) stands at 1.13 inches. Areas north of I-70 are much drier with amounts closer to half an inch, while south of I-70 amounts of 1-4 inches are common. At this point there has been very little snow in December, although that is about to change soon.

The latest NWS outlooks for January and the rest of winter are shown below (click to enlarge).

The temperature forecast for both January and the January-March period show almost all of Illinois with a higher chance of below-average temperatures. Only far northern Illinois escapes this forecast. On the other hand, precipitation has a higher chance of being below average across Illinois and the Great Lakes region. In most cases, these long-range forecasts only nudge the temperature by a few degrees. So, there is still little sign that this winter will be as severe as last.

The NWS does not issue a winter snowfall forecast. And, a combination of colder temperatures and less precipitation does not always translate into less snow. Many times colder weather produces lighter fluffy snow that accumulates but has less water content. We saw a lot of that last winter. However, even if this forecast of colder and drier conditions captures the overall pattern of this winter, we could still see some significant winter storms. Be prepared.

February 1, 2013

January in Illinois – Wet Despite the Lack of Snow

The preliminary numbers are in and the statewide precipitation was 3.9 inches, 1.9 inches above average. Most of the state was in the 3 to 6 inch range except for some drier areas in central and western Illinois. It was wettest in southeastern Illinois with several sites with over 6 inches, including Smithland Lock and Dam on the Ohio River with 9.7 inches. By the way, the precipitation amount includes both rain events and the water equivalent of any snow.
Snowfall for January was below average and ranged from 6.5 inches in the northwest corner to zero in far southern Illinois (second map).
Even though January finished with below-average snowfall, it was offset with above-average rainfall in many areas. The impact of these rains were discussed in an earlier post. As a result, the U.S. Drought Monitor has reduced the area in drought or abnormally dry conditions since January 1 (last figure) by 11 percent.
The statewide temperature for January was 28.7 degrees, four degrees above average. It was far short of the warmest January on record that was established in 2006 with 37.9 degrees and followed closely by 1933 with 37.7 degrees.

January precipitation (rain plus water content from snowfall).

Change in the US Drought Monitor for Illinois through January 2013.