Historical Climate Data

Precipitation Summary

Station: 110338 AURORA, IL

1971-2000 NCDC Normals

Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
Prec. (in) 1.62 1.52 2.57 3.88 3.91 4.34 4.39 4.38 3.50 2.71 3.17 2.40 38.39

Precipitation Extremes

Period of Record: 1887-2006


Month
High (in)
Year
Low (in)
Year 		1-Day
Max (in)
Date
Jan 6.93 1897 0.07 1981 2.91 01-12-1960
Feb 5.79 1997 0.00 1987 3.26 02-21-1997
Mar 6.12 1920 0.33 1994 3.51 03-19-1948
Apr 8.38 1909 0.39 1901 3.52 04-28-1959
May 9.48 1899 0.56 1934 3.59 05-10-1990
Jun 13.19 1902 0.48 1922 4.38 06-24-1994
Jul 21.50 1996 0.41 1937 16.91 07-18-1996
Aug 14.49 1972 0.32 1893 7.12 08-26-1972
Sep 10.97 1961 0.00 1979 6.10 09-13-1978
Oct 14.86 1954 0.24 1964 10.48 10-10-1954
Nov 7.89 1985 0.06 1904 2.74 11-11-1995
Dec 6.30 1949 0.12 1893 2.83 12-19-1895
             
Annual 51.49 1972 21.22 1893 16.91 07-18-1996
Winter 13.15 1950 1.16 1977 3.26 02-21-1997
Spring 15.91 1973 2.59 1934 3.59 05-10-1990
Summer 27.90 1996 4.15 1991 16.91 07-18-1996
Fall 18.02 1941 2.67 1956 10.48 10-10-1954

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 9.7 4.7 0.6 0.2
Feb 7.7 4.1 0.7 0.2
Mar 10.1 5.6 1.7 0.4
Apr 11.7 7.4 2.6 1.1
May 11.2 7.4 2.7 1.2
Jun 9.9 7.2 2.9 1.2
Jul 8.9 5.9 2.5 1.3
Aug 10.0 6.9 2.8 1.2
Sep 8.5 5.3 1.9 0.8
Oct 8.8 5.1 1.9 0.6
Nov 10.1 5.9 2.0 0.9
Dec 10.7 5.2 1.2 0.5
         
Annual 117.2 70.6 23.5 9.4
Winter 28.0 13.9 2.5 0.9
Spring 33.0 20.4 7.0 2.7
Summer 28.8 20.0 8.2 3.7
Fall 27.3 16.3 5.8 2.2

Temperature Summary

Station 110338 AURORA, IL

1971-2000 NCDC Normals

Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
High °F 29.4 34.9 46.4 59.3 71.5 80.7 84.2 82.1 75.2 63.1 47.2 34.2 59.0
Low °F 10.5 15.6 26.1 36.2 46.4 55.7 60.6 58.4 49.9 38.2 27.7 16.4 36.8
Mean °F 20.0 25.3 36.3 47.8 59.0 68.2 72.4 70.3 62.6 50.7 37.5 25.3 48.0
HDD 1397 1113 890 519 237 40 8 27 120 448 828 1232 6859
CDD 0 0 0 1 49 136 237 189 46 3 0 0 661

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

Temperature Extremes

Period of Record: 1887-2006


Month 		High
Mean °F
Year 		Low
Mean °F
Year 		1-Day
Max °F
Date 		1-Day
Min °F
Date
Jan 35.3 2006 7.8 1893 70 01-04-1895 -26 01-20-1985
Feb 38.5 1998 12.2 1936 72 02-25-2000 -25 02-13-1905
Mar 48.7 1945 23.4 1960 83 03-29-1986 -15 03-08-1943
Apr 56.3 1915 40.4 1907 92 04-11-1930 8 04-15-1890
May 67.1 1977 52.4 1907 104 05-31-1934 21 05-10-1966
Jun 76.0 1921 62.5 1916 106 06-01-1934 32 06-08-1888
Jul 81.5 1921 68.5 1924 111 07-14-1936 40 07-03-1907
Aug 78.6 1947 64.8 1915 105 08-09-1934 37 08-31-1915
Sep 70.9 2005 56.0 1918 103 09-14-1939 21 09-27-1893
Oct 62.2 1963 41.9 1917 92 10-01-1897 11 10-28-1925
Nov 48.9 2001 30.7 1976 81 11-01-1950 -11 11-30-1947
Dec 38.7 1889 14.0 2000 69 12-05-2001 -25 12-26-1914
                 
Annual 54.4 1931 41.9 1888 111 07-14-1936 -26 01-20-1985
Winter 33.5 1890 15.8 1977 72 02-25-1900 -26 01-20-1985
Spring 54.3 1977 43.9 1888 104 05-31-1934 -15 03-08-1943
Summer 76.7 1921 66.0 1915 111 07-14-1936 32 06-08-1988
Fall 57.8 1931 46.2 1976 103 09-14-1939 -11 11-30-1947

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 16.9 29.8 7.2
Feb 0.0 10.6 25.5 4.1
Mar 0.0 2.9 22.6 0.2
Apr 0.1 0.1 8.3 0.0
May 0.7 0.0 0.8 0.0
Jun 4.5 0.0 0.0 0.0
Jul 6.4 0.0 0.0 0.0
Aug 4.2 0.0 0.0 0.0
Sep 1.5 0.0 0.3 0.0
Oct 0.0 0.0 6.5 0.0
Nov 0.0 2.1 19.3 0.1
Dec 0.0 11.6 28.6 3.6
         
Annual 17.9 43.8 141.7 15.2
Winter 0.0 39.2 83.9 14.9
Spring 0.8 2.9 31.4 0.2
Summer 15.1 0.0 0.0 0.0
Fall 1.6 2.1 26.4 0.1

Snowfall Summary

Station: 110338 AURORA, IL

1971-2000 Averages

Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
Snow (in) 9.9 7.0 3.4 0.7 0.0 0.0 0.0 0.0 0.0 0.1 1.4 8.3 30.8

Snowfall Extremes

Period of Record: 1887-2006

Month High (in) Year 1-Day Max (in) Date
Jan 32.0 1918 14.0 01-26-1967
Feb 23.6 1908 15.0 02-18-1908
Mar 17.0 1913 12.0 03-25-1913
Apr 13.0 1938 8.0 04-06-1938
May 1.3 1907 1.3 05-03-1907
Jun 0.0 - - -
Jul 0.0 - - -
Aug 0.0 - - -
Sep 0.2 1942 0.2 09-25-1942
Oct 3.9 1967 2.8 10-23-1929
Nov 8.1 1955 7.5 11-27-1975
Dec 36.4 1951 12.0 12-27-1988
Season (Jul-Jun) 62.4 1951-1952 15.0 02-18-1908

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 4.6 2.8 1.5 0.2
Feb 4.6 2.8 1.5 0.2
Mar 2.2 1.3 0.6 0.1
Apr 0.5 0.2 0.1 0.1
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 0.1 0.0 0.0 0.0
Nov 1.2 0.5 0.2 0.0
Dec 5.2 2.5 1.7 0.3
Annual 20.3 10.7 6.0 1.1

Growing Season Summary

Station: 110338 AURORA, 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 3 13 92 288 628 883 1042 977 711 375 100 13 4979
45 0 3 48 176 474 733 887 823 562 243 50 5 3895
50 0 0 23 93 329 583 732 668 416 141 21 2 2928
55 0 0 8 43 204 434 577 514 279 68 7 0 2081
60 0 0 2 18 110 293 423 360 165 26 1 0 1364
50** 2 9 62 176 388 576 704 653 447 229 58 7 3220

**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 4/30 3/28 4/08 5/16 5/28 10/10 9/22 9/26 10/19 10/26
30 4/25 3/28 4/08 5/09 5/18 10/14 9/23 10/02 11/03 11/13
28 4/10 3/27 4/05 4/25 5/07 10/18 9/23 10/05 11/10 11/17
24 4/05 3/19 3/23 4/16 4/27 11/03 10/02 10/16 11/17 11/20
20 3/21 2/23 3/09 4/09 4/10 11/12 10/02 10/30 11/29 12/04
16 3/13 2/14 2/20 4/02 4/09 11/22 10/30 11/07 12/14 1/03

Length of Growing Season (Days)

Derived from 1971-2000 Averages

Temp °F Median Shortest 10% 90% Longest
32 164 124 145 177 196
30 172 140 153 196 206
28 192 150 171 209 222
24 214 176 190 226 245
20 229 191 209 258 269
16 258 222 231 282 302

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