Memorial Day Weekend Rains Push Illinois Records

More rain fell over Illinois over the Memorial Day weekend. The heaviest amounts were in the central part of the state and ranged from 2 to 6 inches (yellow to dark red in the map below).

Right now the statewide average rainfall for May stands at 5.03 inches, based on preliminary data. More rain is forecasted for today and much of this week. So this total is likely to increase as we go through the week. By contrast, Illinois received only 2.5 inches in May 2012.

Click to enlarge.
Click to enlarge.

More Discussion on the Warm March

I have collected several discussions from NWS offices and elsewhere about the warm March and why it happened. Most of these reports offer more details about specific locations. The technical report goes into considerable detail about the underlying meteorological conditions.

In a nutshell (I always think of the Austin Power’s movie when I say that), March 2012 was dominated by unusually strong and steady flow of warm, moist air out of the Gulf of Mexico. That is in sharp contrast to a typical March where we swing back and forth between winter and spring-like temperatures as cold fronts and warm fronts often move through the state.

In fact, from a national perspective the widespread warm March has drawn comparisons to March 1910. See for yourself how these two compared.

March 1910 temperature departures for the U.S. Click to enlarge.
March 2012 temperature departures for the U.S. Click to enlarge.

Record Setting March

March Temperature

The statewide average temperature for March in Illinois was 54.9 degrees, 13.8 degrees above normal. That makes it the warmest March on record. So here are the ten warmest March’s in the Illinois statewide records that date back to 1895:

  1. 2012: 54.9°F
  2. 1946: 51.6°F
  3. 1910: 50.9°F
  4. 1945: 50.5°F
  5. 1921: 49.1°F
  6. 1938: 48.1°F
  7. 2007: 47.6°F
  8. 1973: 47.5°F
  9. 1907: 47.0°F
  10. 1918: 46.4°F

The warmest temperature report in the state was Chicago O’Hare on March 21 with 87 degrees. The coldest temperature report was Monmouth on March 5 with 5 degrees. 

January-March Temperature

The statewide average temperature for January-March in Illinois was 40.9 degrees, 9.1 degrees above normal. That makes it the warmest January-March on record.  Here you will notice that the 2000s are on the list three times as are the 1990s.

  1. 2012: 40.9°F
  2. 1921: 39.2°F
  3. 1990: 38.7°F
  4. 1946: 38.1°F
  5. 1938: 37.6°F
  6. 1998: 37.3°F
  7. 1992: 36.9°F
  8. 2006: 36.7°F
  9. 2000: 36.7°F
  10. 1973: 35.9°F

March Precipitation

The statewide average precipitation was 2.11 inches, 1.1 inches below normal or 66 percent of normal. The statistics are nothing like the March temperatures, but it did end up being the 31st driest March on record for Illinois. Precipitation was below normal across much of the state. However, there were a few wet spots with Fairview Heights (IL-SC-16) reporting the highest monthly total of 4.88 inches of precipitation. Here are the maps of accumulated precipitation and the departure from normal for March in Illinois.

March 2012 precipitation in Illinois. Click to enlarge.
Precipitation departure from normal for March 2012 in Illinois. Click to enlarge.

March Snow

With all the attention on the record warmth, it’s hard to remember that we did see snow in March. The largest monthly total was reported at Roscoe (IL-WN-2) with 5.6 inches of snow.

March 2012 snowfall in Illinois. Click to enlarge.

On Track for Record Setting March

March

[updated March 30, 2012]

Based on data through March 29, the statewide average temperature was 54.7 degrees, 14.1 degrees above normal. Of course, we still have March 30-31 to go but all indications are that the much above normal temperatures will continue. So here are the ten warmest March’s in the Illinois statewide records that date back to 1895:

  1. 2012: 54.7°F (as of March 29)
  2. 1946: 51.6°F
  3. 1910: 50.9°F
  4. 1945: 50.5°F
  5. 1921: 49.1°F
  6. 1938: 48.1°F
  7. 2007: 47.6°F
  8. 1973: 47.5°F
  9. 1907: 47.0°F
  10. 1918: 46.4°F

January-March

Here are the ten warmest January-March’s in the Illinois statewide records. In this case, 2012’s hold on first place is more tenuous. Here you will notice that the 2000s are on the list three times as are the 1990s.

  1. 2012: 40.8°F (as of March 29)
  2. 1921: 39.2°F
  3. 1990: 38.7°F
  4. 1946: 38.1°F
  5. 1938: 37.6°F
  6. 1998: 37.3°F
  7. 1992: 36.9°F
  8. 2006: 36.7°F
  9. 2000: 36.7°F
  10. 1973: 35.9°F

Seventh Wettest Spring on Record for Illinois

The statewide average rainfall of 5.6 inches in May, combined with the 2.8 inches in March and 7.3 inches in April, resulted in a total rainfall for this spring at 15.7 inches. That makes it the seventh wettest spring on record since 1895 and 4.3 inches above average.

The heaviest spring rains fell in southern Illinois. Cairo reported the highest total rainfall with 30.90 inches, followed by Brookport Dam with 29.19 inches, Du Quoin with 28.95 inches, and Carbondale with 27.59 inches. These numbers are slightly more than double the average spring rainfall totals.

[update June 7] I just found a CoCoRaHS observer near Anna (IL-UN-3) who reported 37.5 inches of rain during those three months. To put that in perspective, the average ANNUAL precipitation for the Anna area is 48 inches.

The statewide average temperature for this spring was 52.0 degrees, which is right on the 1971-2000 average of 52.0 degrees.

Note about “spring”: in climatology, we define spring as March – May. This definition lines up better with our ideas of spring weather than the astronomical definition of March 20 (equinox) to June 21 (solstice). In much of Illinois, spring weather starts to arrive before March 20 and summer weather starts to arrive before June 21.

Total rainfall for March-May, 2011, in Illinois.
Total rainfall for March-May, 2011, in Illinois. Click to enlarge.
Rainfall departure for March-May, 2011, in Illinois.
Rainfall departures for March - May 2011, in Illinois. Click to enlarge.

Record Low Pressure on Great Lakes Storm

According to the National Weather Service

New record set today for the lowest pressure in a non-tropical storm in the mainland U.S. The massive storm system barreling across the central U.S. had a minimum central pressure of 28.24″ or 956 mb (equivalent to the minimum pressure of a Category 3 hurricane). This breaks the old record of 28.28″ (958 mb), set on Jan. 26, 1978, during the Blizzard of 1978 (aka the Cleveland Superbomb). This is also lower than the March 1993 Superstorm (aka “The Storm of the Century”), or the “Witch of November” storm that sank the Edmund Fitzgerald in 1975, or even the Columbus Day Storm of Oct. 1962.

Historical Record High Temperatures

With the recent warm weather, have you wondered what the record high temperatures are for Chicago and elsewhere? In the last few years, a group composed of NWS, Regional Climate Centers, and State Climatologists stitched together the weather records for 270 major metropolitan areas. The results of this project can be found at http://threadex.rcc-acis.org/

The sites in Illinois include Chicago, Moline, Peoria, Rockford, and Springfield. Amongst other things, the program reports the daily record high and low temperature and precipitation.

Here I selected the record highs for Chicago and pulled out the results for September. The program gives you the top three candidates and their dates.

Threaded Climate Extremes for Chicago Area, IL
Period of record: 1872 - 2009
Date	Highest Maximum Temperatures (degrees F)
Top 	Record		2nd Record	3rd Record
9/1	101 in 1953	96 in 1984	95 in 1960+
9/2	101 in 1953	98 in 1922	97 in 1913
9/3	97 in 1953	95 in 1960	95 in 1947
9/4	95 in 1983	95 in 1960	95 in 1954
9/5	98 in 1899	97 in 1954	95 in 1983+
9/6	97 in 1960	97 in 1954	96 in 1990+
9/7	100 in 1960	100 in 1939	99 in 1985
9/8	96 in 1960	96 in 1959	96 in 1933+
9/9	95 in 1983	95 in 1959	95 in 1955
9/10	95 in 1983	94 in 1964	94 in 1931+
9/11	95 in 1952	92 in 1908	92 in 1895
9/12	96 in 1952	94 in 1939	93 in 1962
9/13	98 in 1939	95 in 1927	94 in 2005+
9/14	99 in 1939	95 in 1927	95 in 1893
9/15	99 in 1939	94 in 1927	92 in 1955
9/16	92 in 1955	92 in 1931	89 in 1948+
9/17	93 in 1955	90 in 1988	90 in 1891
9/18	94 in 1955	92 in 1953	90 in 1963+
9/19	93 in 1955	92 in 1963	92 in 1948
9/20	91 in 1931	91 in 1895	90 in 1980+
9/21	92 in 1970	90 in 1931	90 in 1924+
9/22	92 in 1956	90 in 1986	90 in 1959+
9/23	91 in 1937	88 in 1892	87 in 1945+
9/24	91 in 1891	90 in 2007	90 in 1920
9/25	90 in 1933	89 in 1920	89 in 1900
9/26	90 in 1998	87 in 1973	86 in 1999+
9/27	91 in 1971	89 in 1987	89 in 1954
9/28	92 in 1953	90 in 1952	89 in 1971
9/29	99 in 1953	87 in 1921	87 in 1898
9/30	92 in 1971	88 in 1943	87 in 1952
+ indicates same value also occurred in a previous year.