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.

August Near-Normal But Summer Hot, Dry for Illinois

August

After months of exceptionally warm temperatures and drought, Illinois finally experienced temperatures and precipitation closer to normal in August.
The statewide average temperature for August was 73.5 degrees, just 0.1 degree below normal. That’s about as “normal” as you can get.
The statewide average precipitation for August was 3.4 inches, which is 95 percent of normal. In the map below, areas in yellow and orange had 3 to 5 inches, while the areas in red had more than 6 inches. Areas in northern and western Illinois in green received less than 2.5 inches. The largest rainfall total in the state was at Grayville in southeast Illinois with 10.69 inches. In second place was Hoopeston with 8.33 inches.

Summer

The statewide average temperature for the three summer months of June, July, and August was 76.1 degrees, 2.6 degrees above normal. It was the eighth warmest summer on record in Illinois. The warmest was 1936 at 78.6 degrees.
The statewide average precipitation for June-August was 6.64 inches, 5.21 inches below normal. It was the sixth driest summer on record in Illinois. The driest was 1988 with 6.17 inches.

Year to Date

The statewide average temperature for January-August was 59.0 degrees, 4.2 degrees above normal. It was the warmest January-August on record in Illinois. The second warmest was 1921 with 58.3 degrees.
The statewide average precipitation for January-August was 17.45 inches, 7.31 inches below normal. It was the fourth driest January-August on record in Illinois. The driest was 1936 with 14.95 inches, followed by 1988 with 17.12 inches, and 1934 with 17.41 inches.

August precipitation for the last 30 days through the morning of August 31. Source: NWS. Click to enlarge.

Long String of Warm, Dry Weather in Illinois

I have updated the plots of statewide monthly temperature and precipitation departures that start in January 2011 and include July 2012. We struggled with dry weather in 2011 but saw some recovery in November and December. However, every month in 2012 has been below normal. In addition, the last three months have shown increasingly larger departures with July being the worst.

Statewide monthly precipitation departures from normal for Illinois. Click to enlarge.

The statewide monthly temperature departures from January 2011 to July 2012 show that 2011 was a moderately warm year with 9 out of 12 months above normal. But the really warm weather (relative to the time of year) started in November 2011 and never really stopped through July of this year.
Statewide average temperature departures from normal for Illinois. Click to enlarge.

No Surprise – July was Hot and Dry for Illinois

July was one of the hottest and driest on record. So was the year to date. Here are how things stack up so far.

How July Ranks

This July was the second warmest and fourth driest on record in Illinois, based on preliminary numbers for the month. The statewide average temperature was 81.8 degrees, 6.4 degrees above normal (1981-2010 average). The statewide average precipitation was 1.47 inches, 2.58 inches below normal or 36 percent of normal.
Statewide Average Temperature Rankings for July in Illinois

  1. 1936:  83.1 ºF
  2. 2012:  81.8 ºF 
  3. 1901:  81.7 ºF
  4. 1934:  81.3 ºF
  5. 1916:  80.4 ºF

Statewide Average Rainfall Rankings for July in Illinois

  1. 1930:  1.02 inches
  2. 1916:  1.23 inches
  3. 1936:  1.24 inches
  4. 2012:  1.47 inches 
  5. 1914:  1.51 inches

I think July 1936 still wins the prize as the most miserable month in Illinois records with the hottest temperatures and the third driest rainfall total. I’m sure 1916 was no fun either as the fifth warmest and second driest July on record. Of course, air-conditioning was pretty much non-existent in 1936. My dad says he remembers sleeping outside that July on the family farm in western Illinois (near Nebo) because the house was too hot.

How the Year-to-Date Ranks

This year so far is the warmest and third driest on record. The statewide average temperature for January-July 2012 was 56.9 degrees, 5.5 degrees above normal. The statewide average precipitation for January-July was 14.05 inches, 9.82 inches below normal or 59 percent of normal.
Statewide Average Temperature Rankings for January-July

  1. 2012:  56.9 ºF
  2. 1921:  56.1 ºF
  3. 1987:  54.1 ºF
  4. 1998:  54.0 ºF
  5. 2006:  53.9 ºF

Statewide Average Precipitation Rankings for January-July

  1. 1936:  12.22 inches
  2. 1934:  13.55 inches
  3. 2012:  14.05 inches
  4. 1988:  14.60 inches
  5. 1914:  15.20 inches

Rainfall Map

This rainfall map was generated by our GIS specialist Zoe and uses NWS radar and rain gauge data. The result is a more detailed picture of the rainfall in July 2012. A few lucky areas in northeastern and far southern Illinois received 2 to 4 inches of rain. Most of the state got an inch or less.

Image courtesy of the Midwestern Regional Climate Center. Click to enlarge.

Bad News for August in Illinois

The NOAA Climate Prediction Center has updated their forecast for August. It’s not good news for Illinois with an increased risk of above-normal temperatures and below-normal precipitation.

NOAA Climate Prediction Center temperature forecast for August, released July 31, 2012. Illinois has a higher risk of above-normal temperatures in August. Click to enlarge.

NOAA Climate Prediction Center precipitation forecast for August, released July 31, 2012. Illinois has a higher risk of below-normal precipitation in August. Click to enlarge.

 

Drought Intensifies in Illinois

The latest U.S. Drought Monitor has expanded D3 “extreme” drought across Illinois. It went from 8 percent of the state last week to 71 percent this week. This major shift was based on a number of short-term drought indicators based on rainfall, streamflow, and temperature, as well as from widespread reports of significant crop and pasture losses.
According to the USDA

The streamlined process provides for nearly an automatic designation for any county in which drought conditions, as reported in the U.S. Drought Monitor … when any portion of a county meets the D2 (Severe Drought) drought intensity value for eight consecutive weeks. A county that has a portion of its area in a drought intensity value of D3 (Extreme Drought) or higher at any time during the growing season also would be designated as a disaster area.

Earlier this week, the USDA NASS reported that 66 percent of the corn crop, 49 percent of the soybean crop, and 91 percent of pasture was rated poor to very poor. Topsoil was rated at 91 percent poor to very poor and subsoil was rated 97 percent poor to very poor. More details can be found in the weekly Illinois Weather and Crops report.

Click to enlarge.

Near Record Heat and Dryness in July

Based on data through yesterday, this July is shaping up to be one of the warmest and driest on record. Based on the forecast, this July is likely to remain as one of the warmest on record. My hope is that we get so much rain in the next week that we are not even close to the driest July on record.
Statewide Average Temperature Rankings for July in Illinois

  1. 1936:  83.1 ºF
  2. 2012:  81.8 ºF (as of July 30)
  3. 1901:  81.7 ºF
  4. 1934:  81.3 ºF
  5. 1916:  80.4 ºF

Statewide Average Rainfall Rankings for July in Illinois

  1. 1930:  1.02 inches
  2. 1916:  1.23 inches
  3. 1936:  1.24 inches
  4. 2012:  1.44 inches (as of July 30)
  5. 1914:  1.51 inches

Higher Risk of Hot, Dry Conditions for August and Fall

The Climate Prediction Center delivered more bad news for Illinois today. Their outlook for August includes an increased chance of above-normal temperatures across Illinois and much of the U.S. It includes an increased chance of below-normal precipitation for all of Illinois and much of the Midwest.
Their outlook for the 3-month period for August-October includes an increased chance of above-normal temperatures for Illinois and much of the eastern two-thirds of the U.S. and below-normal precipitation for Illinois and much of the Midwest.

NOAA Climate Prediction Center outlooks for August and August-October. Click to enlarge. 

Comparison of 2012 to 1988 in Illinois

Precipitation

The first figure shows the statewide precipitation departures by month for both 1988 (blue) and 2012 (red) in Illinois, using the 1981-2010 average as normal. There are several interesting features:

  • the period from January to March was actually drier in 2012 than 1988;
  • the 1988 drought started abruptly in April with dramatically less precipitation; April 2012 was dry but less so than February or March;
  • the precipitation departures in May and June of 1988 were slightly more severe (1/2 inch drier for each month) than 2012;
  • by the end of June, the precipitation deficit was 7.83 inches in 1988 and 7.25 inches in 2012;
  • while less severe than June, precipitation continued to be below normal from July to October in 1988; real relief did not arrive until November.
    Monthly precipitation departure in Illinois for 1988 (blue) and 2012 (red). Click to enlarge.

Temperature
The next figure shows the statewide temperature departures by month for both 1988 (blue) and 2012 (red) in Illinois. There are several interesting features here as well:

  • temperatures from January to March in 2012 were much warmer than normal while they were much cooler than normal in 1988; in fact, January and February was significantly colder in 1988;
  • temperatures in April, May, and June were all above normal in 2012;
  • it wasn’t until May that temperatures in 1988 started to be warmer than normal;
  • warmer than normal temperatures continue in 1988 until October.
Monthly temperature departures in Illinois for 1988 (blue) and 2012 (red). Click to enlarge.

Summary

In summary, the 1988 drought started later than the 2012 drought, but once started it was more intense in the April-June period. However, temperatures were much warmer in 2012 than in 1988. In my opinion, those two factors balance out, making the the 1988 and 2012 very comparable at this point.
How is July unfolding? For the first 17 days of July, the precipitation amounts are identical between 1988 and 2012 at 0.8 inches (40% of normal for that period). However, temperatures for the first 17 days of July 1988 averaged 79.1 degrees, 3.3 degrees above normal. For this July, the average temperature was 82.3 degrees, 6.5 degrees above normal.

First Half of July – Hot and Dry

Rainfall

The statewide average rainfall for Illinois in the first half of July is only 0.8 inches. That is 1.2 inches below average or 40 percent of average. The statewide 1981-2010 average rainfall for the first half of July is 2.0 inches.
The driest July on record was July 1930 with only 1.01 inches. Next in line was 1916 with 1.23 inches and 1936 with 1.24 inches. More recently, 1983 came in 12th place with 1.93 inches and 1988 came in 25th place with 2.60 inches.

Temperature

The statewide average temperature for the first half of July was 82.0 degrees, 6.2 degrees above average. The hottest July on record was 1936 at 83.1 degrees.
Based on preliminary data, there have been 186 new daily records set in July so far and another 33 tied previous records. You can check out the records yourself at http://www.ncdc.noaa.gov/extremes/records/.