Warm, Dry December Concludes a Cold, Wet Year

December temperatures were well above the long-term average across the state, breaking dozens of local daily maximum and minimum temperature records. The preliminary statewide December average temperature was 35.2 degrees, about 5 degrees above the 1981-2010 normal and the 18th warmest on record. Preliminary data show December was drier than average for most of the state. The statewide average December precipitation total was 2.03 inches, 0.66 inches below the 30-year normal.

Data are provisional and may change slightly over time

Warm Weather

Temperatures during the first half of December were very close to average. This was followed by a brief period of well below average temperatures caused by cold air incursion from the north on the back of a strong upper atmosphere trough to our west. On December 20 the predominant wind direction changed to southwesterly, bringing warm, dry air into the region. Temperatures between December 20 and 29 ranged from 5 to 25 degrees above normal across the state. In total, 104 daily high maximum temperature records and 27 daily high minimum temperature records were broken over this time period, including a few dozen records on December 25. In fact, it was the warmest Christmas day at 68 stations across the state. As shown in the figure below, the daily average temperature in Decatur in Macon County on Christmas was nearly 20 degrees above the 30-year normal.

The station in Elgin (Kane County) broke its previous Christmas day high maximum record by 10 degrees. The highest temperature recorded in the state was 70 degrees on December 26 in Wayne County and again on December 29 in Pope County. The lowest temperature was -4 degrees on December 15 in Rock Island County.

A shift in the upper atmosphere and the passage of a cold front late in the month allowed temperatures to moderate. December average temperatures ranged from the low 30s in northern Illinois to the mid-40s in southern Illinois. Monthly average temperature departures ranged from 7 degrees above the long-term mean in northwestern Illinois to just over 1 degree above average in south-central Illinois.

The preliminary 2019 statewide average December temperature was 35.2 degrees, which was the 18th warmest December on record. December’s warm weather was an aberration in an otherwise colder than average 2019 in Illinois. Only three months this year–July, September, and December–exhibited a statewide average temperature above the 30-year normal.

Precipitation

December precipitation was below the long-term average for the entire state. Areas in far southern Illinois received 2 to 3 inches less than average in December, approximately 50 percent of normal December precipitation. The statewide average total December precipitation was 2.03 inches, approximately 0.66 inches below normal. This last month was the 50th driest December on record in Illinois and marked the second straight month of below average statewide precipitation. Preexisting wetness and reduced evaporative demand, typical for this time of the year, have prevented impacts from the prolonged dry conditions. Despite two straight months of well below average precipitation, streamflow and soil moisture were both near normal across the state.

Snowfall totals this last month ranged from less than a tenth of an inch in far southern Illinois to over 10 inches in south-central Illinois. A strong system came through in mid-December and brought several inches of snow to an area spanning the St. Louis Metro East to the Champaign-Urbana area. The highest 24-hour snowfall total was 5.6 inches in Lovington (Moultrie County) on December 17, although CoCoRaHS observers in Mascoutah in St. Clair County and Columbia in Monroe County both recorded 7.5 inches on December 17.

The December snowfall glut in south-central Illinois turned into snowfall deficits of 8 to 10 inches in northern Illinois. This last month was only the 10th December with 1 inch or less of snowfall in Stockton (Jo Daviess County). Despite the small snowfall totals this last month, the seasonal total snowfall was above average for most of the state between interstates 80 and 64. A broad area between Peoria and the St. Louis metro east received over 4 inches of above average snowfall, whereas the Chicagoland region has so far this season experienced a snowfall deficit of 4 to 6 inches.

Outlooks

Short-term 8-14-day outlooks from the NOAA Climate Prediction Center show strongly elevated odds of both above normal precipitation and above normal temperature.

Thirty-day outlooks show elevated odds of wetter and warmer than normal conditions to persist throughout January in southern Illinois. Outlooks for January through March and March through May continue to show elevated odds of above normal precipitation for the entire state.

Second Coldest April on Record in Illinois

Temperature
Based on the official data, the statewide average temperature was  44.5 degrees,  8.1 degrees below normal. It was the second coldest April on record, only beaten by 43.1 degrees set in April 1907. Our statewide records go back to 1895. Normal refers to a specific benchmark, the 1981-2010 average. See the longer explanation here.
Here are the temperature departures from normal look like across the Midwest. Areas in green are 1 to 9 degrees below normal, while areas in icy blue are 9 or more degrees below normal. The lowest temperature reported in Illinois for April was -1 at both Avon and Lincoln on April 2. At the other extreme, we did reach into the 80s at times during the month. The warmest reading was 86 degrees at Kaskaskia on April 13.
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Precipitation Continue reading “Second Coldest April on Record in Illinois”

5th Warmest November, 2nd Warmest Fall in Illinois

Temperature

This was the 5th warmest November on record for Illinois, based on preliminary data. The statewide average temperature was 47.4 degrees, and 4.9 degrees above normal. Here are the top ten warmest Novembers in Illinois since 1895:

  1. 2001 with 49.9°F
  2. 1931 with 49.1°F
  3. 1909 with 48.8°F
  4. 1999 with 48.4°F
  5. 2016 with 47.4°F 
  6. 2009 with 47.2°F
  7. 1902 with 46.9°F
  8. 1990 with 46.8°F
  9. 2015 with 46.6°F
  10. 1913 with 46.4°F

It was also the 2nd warmest fall on record for Illinois. The statewide average temperature for fall was 59.4 degrees, 5 degrees above normal. Only the fall of 1931 was warmer at 59.8 degrees. The climatological fall months are September, October, and November.

Precipitation

Continue reading “5th Warmest November, 2nd Warmest Fall in Illinois”

Average Date of First Snow in Illinois

I have noticed that the average date of the first snow is a popular search term on the blog, so here is the reposting of the median dates of the first measurable snowfall of the season in Illinois. This map is based on 1971-2000 data. While it is not based on the current 1981-2010 averages, the map is still relevant for the purpose of getting an idea of the dates. Measurable snowfall means at least a tenth of an inch.

Median Date:

In the northern third of Illinois, the first snowfall occurred around Thanksgiving. The dates switch from November to December once you reach central Illinois (just north of a line between Quincy and Champaign). By the time you reach Carbondale, the date can be as late as December 20. From this you can see that we are by no means behind schedule this year.

date of first snow

Early Date:

Continue reading “Average Date of First Snow in Illinois”

Widespread Heavy Rain Expected this Week

The rain has finally moved into Illinois this morning. According to the National Weather Service, widespread heavy rain is expected to continue in Illinois over the next 3 days. Here is the forecast map for Tuesday morning showing a large storm moving across the central US. Rain is likely from the Gulf of Mexico all the way up to the western Great Lakes. Snow is likely in the Plains states (areas in blue). However, we will likely be too warm in Illinois to see snowfall.

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Forecast map for Tuesday morning. Dark green means that rain is likely. The blues back in Colorado, Kansas, and Nebraska means snows. Source: NWS.

Continue reading “Widespread Heavy Rain Expected this Week”

After Slow Start to Snow Season, Illinois Catching Up

After a slow start to the snowfall season in Illinois, we are now catching up. Heavy snow fell across northern Illinois over the weekend and more snow is arriving today.

The Chicago NWS office has a nice write-up on the recent historic winter storm that stretched all the way across Illinois and into Indiana. We can call it a historic winter storm because it was the fifth largest in Chicago history with 19.3 inches reported at O’Hare airport.

Here are our snowfall departure from average as of a week ago and as of this morning. Northern Illinois went from a deficit of 1 to 8 inches to a surplus of 1 to 8 inches in green and 8 or more inches in blue. And more snow is falling as I write this so some of the deficits across central Illinois may be erased soon.

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Snowfall departure from average as of January 29, 2015. Click to enlarge.
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Snowfall departure from average as of February 4, 2015. Click to enlarge.

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”

Friday Wrapup – Illinois Very Cold and Dry in November

snow-nov21So far, November has been much colder and drier than average. The statewide average temperature is 34.6 degrees, which is 9 degrees below average.

The statewide average precipitation (rainfall + water content of snow) was only 0.6 inches, about a third of the average through this date.

There have been astounding snowfall totals in places like Buffalo, NY, and some significant snowfall in Minnesota and Wisconsin. However, Illinois and most of the surrounding states have had far less snowfall (first map) in November. Many sites in the state had 1 to 2 inches except for a stretch between Quincy and Chicago with less than an inch.

The modest snowfall totals in November so far are not that unusual. Average snowfall totals for the month are generally less than an inch south of I-80 and about 1 to 2 inches north of I-80 (second map).

map2Illinois-snow-11NOV-normals

Cold and Snowy November in Illinois

snow-nov17-2014-smallHere is the scene out my backdoor last night, not just frost on the pumpkin but real snow. And the poor annuals in the flower-pot are done.

As of this morning we had 0.5 inches of snow in Champaign-Urbana. The snow over this weekend was widespread across Illinois but heaviest in the far north and far south (map below). In fact, the heaviest amounts were in southern and eastern Illinois and included Shawneetown with 4.0 inches, Newton with 3.1 inches, and Beecher City, Paris, and Salem all with 3.0 inches.  Nationally, 50 percent of the US is covered in snow this morning (second map). snow-novThe statewide average temperature for Illinois for November is 37.7 degrees, 6.5 degrees below average. Both Chicago and Rockford have experienced 5 days in a row with temperatures not rising above freezing. And the National Weather Service forecasts for today and Tuesday show that highs will stay in the teens in northern Illinois and in the 20’s in central and southern Illinois. Those are temperatures more typical of January than November. Temperatures are expected to slowly warm up towards the weekend.

nsm_depth_2014111705_National
Fifty percent of the lower 48 states covered in snow.

Champaign-Urbana Winter Weather Stats

Below is a summary of the February and winter weather statistics for Champaign-Urbana:

February

  • The average temperature for February was 19.0 degrees, which was 9.9 degrees below average and the 9th coldest on record.
  • The total snowfall for February was 14.6 inches, which was 8.8 inches above average and the 10th snowiest on record.

Winter

  • The average temperature for the three core winter months of December, January, and February, was 21.6 degrees, which was 8.6 degrees below average and the 9th coldest on average.
  • Our seasonal snowfall total that goes all the way back to November, was 41.1 inches as of March 3. That makes it the 7th snowiest seasonal total on record and 17.9 inches above the seasonal average of 23.2 inches.

It was certainly a cold and snowy winter but it was hard to beat those winters in the late 1970s and early 1980s. For example, the winter of 1977-78 experienced the most snow in Champaign-Urbana history with 67.2 inches. It was also the coldest during the December-February period at 20.2 degrees.

The official NWS cooperative observer site is located at the Illinois State Water Survey near the corner of First and Windsor in Champaign.