Historical Climate Data

Precipitation Summary

Station: 116910 PONTIAC, IL

1971-2000 NCDC Normals

Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
Prec. (in) 1.63 1.44 2.82 3.41 3.83 4.11 4.07 3.56 3.04 2.67 3.02 2.51 36.11

Precipitation Extremes

Period of Record: 1890-2006


Month
High (in)
Year
Low (in)
Year 		1-Day
Max (in)
Date
Jan 6.35 1916 0.00 1984 1.97 01-02-1965
Feb 4.52 1908 0.04 1987 2.55 02-06-1942
Mar 6.08 1923 0.20 1910 3.80 03-12-1923
Apr 10.09 1957 0.37 1971 2.70 04-27-1943
May 10.03 1995 0.45 1934 4.76 05-11-1962
Jun 11.60 1973 0.27 1988 5.67 06-17-1973
Jul 8.87 1958 0.26 1940 4.26 07-17-1950
Aug 8.65 1977 0.31 1984 5.59 08-03-1943
Sep 11.83 1961 0.05 1979 4.25 09-26-1933
Oct 11.58 1941 0.07 1964 2.96 10-23-1957
Nov 8.18 1985 0.06 1904 4.42 11-28-1990
Dec 8.72 1982 0.25 1890 5.50 12-03-1982
             
Annual 48.96 1993 21.13 1963 5.67 06-17-1973
Winter 12.88 1950 1.52 1961 5.50 12-03-1982
Spring 20.18 1944 2.96 1958 4.76 05-11-1962
Summer 20.59 1993 2.85 1920 5.67 06-17-1973
Fall 18.30 1926 2.64 1963 4.42 11-28-1990

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 8.4 4.5 0.9 0.2
Feb 7.1 3.8 0.7 0.2
Mar 9.7 6.7 1.9 0.5
Apr 11.0 7.4 2.5 0.6
May 11.3 7.9 2.9 0.9
Jun 9.6 6.7 2.8 1.2
Jul 8.9 6.3 2.9 1.1
Aug 8.3 6.0 2.2 1.0
Sep 8.0 5.1 2.2 0.9
Oct 8.3 5.3 2.0 0.5
Nov 9.9 6.3 1.9 0.5
Dec 9.5 5.3 1.6 0.5
         
Annual 110.1 71.3 24.7 8.0
Winter 25.1 13.6 3.3 0.8
Spring 32.0 21.9 7.3 1.9
Summer 26.8 19.1 7.9 3.3
Fall 26.1 16.6 6.1 1.9

Temperature Summary

Station 116910 PONTIAC, IL

1971-2000 NCDC Normals

Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
High °F 29.9 35.7 48.2 61.5 73.1 82.1 84.7 82.7 77.0 64.8 48.7 35.4 60.3
Low °F 13.8 18.3 28.6 38.7 49.6 59.8 63.6 61.7 53.5 41.9 31.0 20.1 40.1
Mean °F 21.9 27.0 38.4 50.1 61.4 71.0 74.2 72.2 65.3 53.4 39.9 27.8 50.2
HDD 1339 1064 825 452 191 19 4 19 80 373 755 1155 6276
CDD 0 0 0 5 77 197 288 243 87 12 0 0 909

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

Temperature Extremes

Period of Record: 1903-2006


Month 		High
Mean °F
Year 		Low
Mean °F
Year 		1-Day
Max °F
Date 		1-Day
Min °F
Date
Jan 38.1 1933 9.2 1977 69 01-23-1909 -24 01-15-1927
Feb 39.7 1930 15.3 1979 72 02-15-1921 -23 02-13-1905
Mar 51.2 1910 24.5 1960 86 03-23-1910 -14 03-08-1943
Apr 58.7 1915 43.6 1907 92 04-11-1930 11 04-07-1982
May 70.4 1977 55.9 1997 102 05-31-1934 24 05-10-1966
Jun 79.6 1934 65.9 1958 105 06-01-1934 38 06-08-1913
Jul 83.8 1936 70.6 1992 108 07-14-1936 45 07-26-1911
Aug 80.6 1947 67.0 1992 104 08-05-1918 40 08-31-1915
Sep 73.1 1931 59.6 1949 103 09-04-1925 26 09-28-1942
Oct 65.8 1963 45.3 1925 94 10-02-1922 9 10-30-1925
Nov 51.4 1931 33.0 1996 82 11-07-1915 -5 11-28-1930
Dec 39.5 1923 14.7 1983 71 12-03-1982 -23 12-28-1924
                 
Annual 56.3 1921 48.1 1989 108 07-14-1936 -24 01-15-1927
Winter 37.2 1932 18.6 1979 72 02-15-1921 -24 01-15-1927
Spring 58.0 1977 45.7 1984 102 05-31-1934 -14 03-08-1943
Summer 78.9 1934 68.5 1992 108 07-14-1936 38 06-08-1913
Fall 61.4 1931 49.2 1976 103 09-04-1925 -5 11-28-1930

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 17.4 29.0 5.6
Feb 0.0 10.3 24.5 3.0
Mar 0.0 3.1 20.0 0.1
Apr 0.0 0.1 6.6 0.0
May 1.0 0.0 0.2 0.0
Jun 4.9 0.0 0.0 0.0
Jul 7.3 0.0 0.0 0.0
Aug 4.6 0.0 0.0 0.0
Sep 2.0 0.0 0.1 0.0
Oct 0.0 0.0 4.3 0.0
Nov 0.0 2.2 16.8 0.0
Dec 0.0 10.8 27.1 2.6
         
Annual 19.9 43.3 127.8 11.2
Winter 0.0 38.3 80.6 11.2
Spring 1.1 3.2 26.8 0.1
Summer 16.8 0.0 0.0 0.0
Fall 2.1 2.2 20.9 0.0

Snowfall Summary

Station: 116910 PONTIAC, IL

1971-2000 Averages

Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
Snow (in) 9.2 5.5 2.9 0.9 0.0 0.0 0.0 0.0 0.0 0.0 1.7 6.1 26.3

Snowfall Extremes

Period of Record: 1890-2006

Month High (in) Year 1-Day Max (in) Date
Jan 30.5 1979 16.0 01-13-1927
Feb 20.0 1994 10.0 02-07-1933
Mar 15.0 1906 8.0 03-25-1930
Apr 12.0 1997 12.0 04-11-1997
May 0.5 1907 0.5 05-04-1907
Jun 0.0 - - -
Jul 0.0 - - -
Aug 0.0 - - -
Sep 2.5 1942 2.5 09-25-1942
Oct 4.0 1929 4.0 10-23-1929
Nov 8.8 1951 7.5 11-06-1951
Dec 27.0 2000 12.0 12-25-1909
Season (Jul-Jun) 49.0 1977-1978 16.0 01-13-1927

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 3.6 1.9 1.1 0.2
Feb 3.6 1.9 1.1 0.2
Mar 1.7 0.9 0.6 0.2
Apr 0.4 0.3 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 0.0 0.0 0.0 0.0
Nov 1.0 0.5 0.4 0.1
Dec 3.8 2.3 1.4 0.2
Annual 15.1 9.1 5.0 1.2

Growing Season Summary

Station: 116910 PONTIAC, 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 7 24 123 343 688 946 1081 1013 773 435 133 23 5552
45 1 8 68 223 534 796 926 858 625 299 72 10 4393
50 0 2 35 129 385 646 771 704 478 185 34 4 3352
55 0 0 15 67 251 497 616 550 337 101 13 1 2431
60 0 0 5 30 143 351 461 396 213 45 3 0 1637
50** 3 15 78 208 423 630 740 685 494 261 74 12 3600

**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 4/19 3/25 4/04 5/06 5/12 10/18 9/23 10/04 11/04 11/06
30 4/13 3/25 4/01 4/28 5/07 10/22 10/02 10/07 11/16 12/02
28 4/09 3/23 3/25 4/20 5/07 11/02 10/02 10/12 11/20 12/02
24 3/25 3/06 3/15 4/11 4/18 11/08 10/20 10/23 11/21 12/11
20 3/18 2/22 3/02 4/09 4/10 11/20 10/24 11/02 12/05 12/11
16 3/12 1/31 2/14 3/25 4/08 12/01 11/02 11/10 12/22 12/24

Length of Growing Season (Days)

Derived from 1971-2000 Averages

Temp °F Median Shortest 10% 90% Longest
32 181 150 160 204 226
30 194 161 173 224 244
28 205 176 182 231 245
24 222 194 206 250 260
20 243 217 220 267 282
16 267 221 239 295 300

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