Historical Climate Data

Precipitation Summary

Station: 112193 DECATUR, IL

1971-2000 NCDC Normals

Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
Prec. (in) 2.05 1.95 3.20 3.58 4.47 3.90 4.54 4.14 2.98 2.74 3.32 2.87 39.74

Precipitation Extremes

Period of Record: 1893-2006


Month
High (in)
Year
Low (in)
Year 		1-Day
Max (in)
Date
Jan 7.47 1907 0.20 1931 2.25 01-03-1950
Feb 5.89 1900 0.14 1947 2.42 02-10-1939
Mar 9.85 1898 0.18 1999 4.25 03-27-1898
Apr 9.71 1957 0.59 1899 3.58 04-12-1979
May 12.57 1943 0.30 1934 4.22 05-19-1974
Jun 10.21 1974 0.53 1933 4.76 06-02-1965
Jul 16.72 1992 0.11 1916 5.11 07-26-1992
Aug 10.97 1981 0.22 1943 4.71 08-02-1978
Sep 16.56 1926 0.02 1979 4.66 09-18-1904
Oct 10.64 1941 0.18 1904 4.09 10-22-1983
Nov 9.07 1992 0.07 1904 3.70 11-02-1936
Dec 8.15 1967 0.21 1930 2.85 12-18-1895
             
Annual 60.58 1927 23.39 1894 5.11 07-26-1992
Winter 16.10 1950 1.71 1931 2.85 12-18-1895
Spring 20.43 2002 4.56 1934 4.25 03-27-1898
Summer 22.95 1981 2.76 1933 5.11 07-26-1992
Fall 25.83 1926 3.35 1956 4.66 09-18-1904

Precipitation Threshold Climatology

Derived from 1971-2000 Averages:

*Annual/seasonal totals may differ from the sum of the monthly totals due to rounding.


Month 		# Days
Total ≥ 0.01" 		# Days
Total ≥ 0.10" 		# Days
Total ≥ 0.50" 		# Days
Total ≥ 1.00"
Jan 9.0 4.9 1.3 0.3
Feb 7.9 4.3 1.2 0.4
Mar 10.5 7.1 2.1 0.5
Apr 11.2 7.2 2.6 0.8
May 10.8 7.1 3.1 1.2
Jun 9.9 6.7 3.0 1.2
Jul 9.2 6.3 3.1 1.3
Aug 7.7 5.5 3.0 1.3
Sep 7.4 4.9 2.2 0.8
Oct 7.9 5.0 1.9 0.7
Nov 9.4 6.4 2.4 0.7
Dec 10.1 5.6 2.0 0.5
         
Annual 110.8 70.8 27.8 9.8
Winter 26.9 14.8 4.4 1.2
Spring 32.5 21.3 7.8 2.6
Summer 26.7 18.5 9.2 3.8
Fall 24.8 16.3 6.4 2.2

Temperature Summary

Station 112193 DECATUR, IL

1971-2000 NCDC Normals

Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
High °F 34.5 40.5 52.6 65.3 76.1 84.5 87.8 85.8 79.9 67.8 52.0 39.2 63.8
Low °F 17.1 22.1 31.9 41.8 51.6 60.6 64.6 62.8 54.9 43.9 33.5 22.6 42.3
Mean °F 25.8 31.3 42.3 53.6 63.9 72.6 76.2 74.3 67.4 55.9 42.8 30.9 53.1
HDD 1215 943 706 350 139 10 0 11 54 305 668 1057 5458
CDD 0 0 0 7 104 237 348 299 125 22 0 0 1142

HDD - heating degree days (base 65F); CDD - cooling degree days (base 65F)

Temperature Extremes

Period of Record: 1893-2006


Month 		High
Mean °F
Year 		Low
Mean °F
Year 		1-Day
Max °F
Date 		1-Day
Min °F
Date
Jan 39.6 2006 11.0 1977 73 01-24-1909 -23 01-17-1977
Feb 41.1 1998 18.3 1978 76 02-29-1972 -25 02-13-1905
Mar 54.3 1946 27.4 1960 89 03-24-1929 -10 03-05-1978
Apr 61.3 1896 43.0 1907 98 04-30-1895 15 04-05-1920
May 71.5 1962 56.5 1907 101 05-31-1934 25 05-14-1895
Jun 80.7 1934 66.3 1903 105 06-30-1931 32 06-06-1894
Jul 84.1 1936 72.2 1971 113 07-14-1954 45 07-02-1904
Aug 82.6 1947 68.8 1927 106 08-09-1934 35 08-29-1986
Sep 74.9 1931 60.5 1918 104 09-05-1954 20 09-30-1899
Oct 66.5 1963 46.5 1925 96 10-02-1953 12 10-30-1925
Nov 52.5 1931 34.4 1976 83 11-01-1933 -3 11-30-1929
Dec 41.2 1931 17.7 1983 72 12-01-1970 -22 12-24-1983
                 
Annual 57.6 1931 48.8 1997 113 07-14-1954 -25 02-13-1905
Winter 39.2 1932 21.0 1978 76 02-29-1972 -25 02-13-1905
Spring 58.4 1977 47.8 1960 101 05-31-1934 -10 03-05-1978
Summer 79.8 1934 70.7 1927 113 07-14-1954 32 06-06-1994
Fall 62.7 1931 50.0 1976 104 09-05-1954 -3 11-30-1929

Temperature Threshold Climatology

Derived from 1971-2000 Averages:

*Annual/seasonal values may differ from the sum of the monthly values due to rounding.


Month 		# Days
High ≥ 90°F 		# Days
High ≤ 32°F 		# Days
Low ≤ 32°F 		# Days
Low ≤ 0°F
Jan 0.0 13.3 27.9 4.3
Feb 0.0 7.3 22.2 2.6
Mar 0.0 1.6 16.7 0.1
Apr 0.0 0.0 5.3 0.0
May 1.9 0.0 0.4 0.0
Jun 7.6 0.0 0.0 0.0
Jul 12.3 0.0 0.0 0.0
Aug 7.8 0.0 0.0 0.0
Sep 3.7 0.0 0.2 0.0
Oct 0.1 0.0 4.5 0.0
Nov 0.0 1.2 15.0 0.0
Dec 0.0 7.2 24.9 1.6
         
Annual 32.9 30.6 117.8 8.7
Winter 0.0 27.8 75.1 8.6
Spring 1.9 1.6 22.7 0.1
Summer 27.5 0.0 0.0 0.0
Fall 4.0 1.2 19.5 0.0

Snowfall Summary

Station: 112193 DECATUR, IL

1971-2000 Averages

Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
Snow (in) 7.7 4.9 2.4 0.4 0.0 0.0 0.0 0.0 0.0 0.0 1.1 5.4 21.9

Snowfall Extremes

Period of Record: 1893-2006

Month High (in) Year 1-Day Max (in) Date
Jan 25.0 1979 10.0 01-13-1927
Feb 18.0 1914 8.0 02-16-1903
Mar 30.5 1906 13.5 03-19-1906
Apr 11.0 1920 4.0 04-05-1920
May 12.2 1929 8.2 05-03-1929
Jun 0.0 - - -
Jul 0.0 - - -
Aug 0.0 - - -
Sep 0.0 - - -
Oct 4.0 1929 4.0 10-23-1929
Nov 13.5 1951 11.0 11-06-1951
Dec 30.5 1973 10.0 12-20-1973
Season (Jul-Jun) 49.7 1981-1982 13.5 03-19-1906

Snowfall Threshold Climatology

Derived from 1971-2000 Averages

*Annual values may differ from the sum of the monthly values due to rounding.


Month 		# Days
Total ≥ 0.1" 		# Days
Total ≥ 1.0" 		# Days
Total ≥ 2.0" 		# Days
Total ≥ 5.0"
Jan 2.8 1.7 1.0 0.3
Feb 2.8 1.7 1.0 0.3
Mar 1.2 0.9 0.6 0.1
Apr 0.3 0.1 0.1 0.0
May 0.0 0.0 0.0 0.0
Jun 0.0 0.0 0.0 0.0
Jul 0.0 0.0 0.0 0.0
Aug 0.0 0.0 0.0 0.0
Sep 0.0 0.0 0.0 0.0
Oct 0.0 0.0 0.0 0.0
Nov 0.5 0.4 0.3 0.0
Dec 2.8 1.9 1.0 0.2
Annual 11.7 7.3 4.3 0.9

Growing Season Summary

Station: 112193 DECATUR, IL

Growing Degree Day Averages

Derived from 1971-2000 Data

Base Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
40 16 48 172 416 735 980 1121 1071 824 494 175 39 5906
45 5 20 98 286 581 830 967 916 674 352 101 17 4700
50 1 7 51 177 430 681 812 762 527 229 52 7 3619
55 0 1 23 95 289 531 658 607 383 133 22 2 2660
60 0 0 8 44 170 383 504 453 252 63 7 0 1826
50** 8 28 107 256 467 656 761 727 538 308 99 21 3856

**Modified Growing Degree Days: Base 50, Ceiling 86.

Growing Season Summary

Derived from 1971-2000 Averages

Date of Last Spring Occurrence Date of First Fall Occurrence
Temp °F Median Early 90% 10% Late Median Early 90% 10% Late
32 4/22 3/29 4/06 5/10 5/25 10/10 9/20 9/25 10/24 11/04
30 4/10 3/26 4/05 5/07 5/12 10/13 9/21 10/01 10/26 11/04
28 4/09 3/20 3/31 4/20 5/07 10/21 10/03 10/07 11/05 11/13
24 4/05 3/05 3/16 4/12 4/18 11/03 10/08 10/15 11/17 11/30
20 3/20 2/08 3/05 4/08 4/10 11/13 10/12 10/25 12/06 12/20
16 3/10 2/08 2/18 3/26 4/07 11/22 11/03 11/07 12/19 12/30

Length of Growing Season (Days)

Derived from 1971-2000 Averages

Temp °F Median Shortest 10% 90% Longest
32 171 136 145 198 204
30 183 149 155 204 212
28 193 170 173 215 221
24 212 187 194 237 260
20 234 191 214 266 288
16 260 222 231 289 311

Back to the Station List

Copyright 2007 Illinois State Water Survey
Jim Angel, State Climatologist, jimangel@illinois.edu
Last Modified: September 11, 2007