Historical Climate Data

Precipitation Summary

Station: 111497 CHICAGO BOTANICAL GARDEN, IL

1971-2000 NCDC Normals

Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
Prec. (in) 1.89 1.56 2.50 3.70 3.59 3.86 3.50 4.84 3.24 2.70 3.22 2.20 36.80

Precipitation Extremes

Period of Record: 1981-2006


Month
High (in)
Year
Low (in)
Year 		1-Day
Max (in)
Date
Jan 4.12 2005 0.39 1986 2.14 01-01-1985
Feb 5.86 1997 0.03 1987 3.20 02-21-1997
Mar 4.58 1985 0.90 1996 2.00 03-04-1985
Apr 8.93 1999 1.06 2005 2.58 04-27-1995
May 9.42 2004 0.59 1992 2.97 05-10-1990
Jun 8.01 1993 0.41 1995 4.50 06-24-1994
Jul 7.85 1982 1.06 1991 3.03 07-18-1996
Aug 13.09 1987 1.19 2003 5.54 08-14-1987
Sep 9.63 1986 0.23 2004 2.56 09-12-2000
Oct 8.25 1991 0.92 2005 3.59 10-03-2006
Nov 7.16 1985 0.38 1999 2.33 11-01-1994
Dec 5.90 1982 0.41 1989 2.79 12-03-1982
             
Annual 47.92 1983 24.35 2005 5.54 08-14-1987
Winter 9.77 1997 1.84 2003 3.20 02-21-1997
Spring 15.63 1983 4.12 2005 2.97 05-10-1990
Summer 19.09 1987 5.80 1991 5.54 08-14-1987
Fall 16.13 2006 5.00 1987 3.59 10-03-2006

Precipitation Threshold Climatology

Derived from 1981-2000 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 9.8 5.4 1.0 0.2
Feb 7.5 3.9 0.7 0.2
Mar 9.9 5.6 1.7 0.3
Apr 12.9 6.9 2.8 0.8
May 11.8 7.6 2.6 0.7
Jun 10.4 6.3 2.4 0.8
Jul 9.5 6.3 2.5 1.2
Aug 9.3 6.3 3.0 1.3
Sep 9.5 6.2 2.1 1.1
Oct 9.8 5.8 1.7 0.6
Nov 10.6 6.2 2.3 0.7
Dec 9.7 5.3 1.1 0.3
         
Annual 120.7 71.8 23.9 8.2
Winter 27.0 14.6 2.8 0.7
Spring 34.6 20.2 7.2 1.8
Summer 29.2 18.9 7.9 3.3
Fall 29.9 18.2 6.1 2.4

Temperature Summary

Station 111497 CHICAGO BOTANICAL GARDEN, IL

1971-2000 NCDC Normals

Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
High °F 30.2 35.0 44.5 55.8 67.4 77.8 83.2 81.3 74.5 63.0 48.5 35.7 58.1
Low °F 13.7 18.1 27.7 36.8 46.7 55.9 62.5 61.7 53.5 41.8 32.1 20.2 39.2
Mean °F 22.0 26.6 36.1 46.3 57.1 66.9 72.9 71.5 64.0 52.4 40.3 28.0 48.7
HDD 1335 1077 897 562 283 67 7 18 96 398 741 1149 6630
CDD 0 0 0 0 36 123 250 221 66 6 0 0 702

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

Temperature Extremes

Period of Record: 1981-2006


Month 		High
Mean °F
Year 		Low
Mean °F
Year 		1-Day
Max °F
Date 		1-Day
Min °F
Date
Jan 35.1 2006 12.6 1982 63 01-05-1997 -27 01-10-1982
Feb 37.6 1998 20.1 1989 74 02-26-2000 -20 02-03-1996
Mar 44.0 2000 28.2 1984 83 03-30-1986 -5 03-04-2002
Apr 52.0 2006 43.1 1982 90 04-19-2002 10 04-07-1982
May 63.6 1991 51.9 1997 93 05-29-1991 28 05-03-2004
Jun 73.0 2005 60.4 1982 102 06-22-1988 37 06-01-1993
Jul 77.1 1999 68.2 1992 105 07-14-1995 45 07-01-1982
Aug 77.4 1995 66.3 1992 101 08-02-1988 42 08-29-1986
Sep 69.0 2005 59.2 1993 97 09-07-1990 30 09-30-1993
Oct 56.6 2000 46.8 1987 88 10-04-1997 24 10-19-1992
Nov 48.5 2001 32.8 1995 76 11-10-1999 6 11-13-1986
Dec 36.5 1982 16.0 1983 70 12-06-2001 -20 12-24-1983
                 
Annual 52.9 1998 46.8 1996 105 07-14-1995 -27 01-10-1982
Winter 33.3 2002 19.8 1982 74 02-26-1900 -27 01-10-1982
Spring 51.0 1991 42.1 1984 93 05-29-1991 -5 03-04-1902
Summer 74.4 1995 65.8 1992 105 07-14-1995 37 06-01-1993
Fall 55.8 1998 49.4 1993 97 09-07-1990 6 11-13-1986

Temperature Threshold Climatology

Derived from 1981-2000 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 16.4 28.6 4.8
Feb 0.0 10.3 24.9 2.1
Mar 0.0 4.7 21.6 0.2
Apr 0.0 0.3 8.1 0.0
May 0.6 0.0 0.4 0.0
Jun 3.5 0.0 0.0 0.0
Jul 5.9 0.0 0.0 0.0
Aug 3.7 0.0 0.0 0.0
Sep 1.5 0.0 0.2 0.0
Oct 0.0 0.0 4.3 0.0
Nov 0.0 2.1 15.3 0.0
Dec 0.0 10.6 27.0 2.1
         
Annual 15.4 44.5 131.0 9.1
Winter 0.0 36.9 80.4 8.8
Spring 0.6 5.0 30.0 0.2
Summer 13.2 0.0 0.0 0.0
Fall 1.5 2.1 19.9 0.0

Snowfall Summary

Station: 111497 CHICAGO BOTANICAL GARDEN, IL

1981-2000 Averages

Element Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann
Snow (in) 10.2 8.2 5.0 1.1 0.0 0.0 0.0 0.0 0.0 0.1 1.7 7.0 33.4

Snowfall Extremes

Period of Record: 1981-2006

Month High (in) Year 1-Day Max (in) Date
Jan 22.6 1997 12.0 01-31-2002
Feb 27.3 1994 10.0 02-15-1990
Mar 15.6 1999 9.5 03-22-1992
Apr 10.2 1982 8.8 04-06-1982
May 0.4 1989 0.4 05-07-1989
Jun 0.0 - - -
Jul 0.0 - - -
Aug 0.0 - - -
Sep 0.0 - - -
Oct 1.6 2006 1.6 10-13-2006
Nov 6.6 1995 5.0 11-21-1996
Dec 31.3 2000 8.0 12-01-2006
Season (Jul-Jun) 47.7 1996-1997 12.0 01-31-2002

Snowfall Threshold Climatology

Derived from 1981-2000 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 4.5 2.7 1.6 0.3
Feb 4.5 2.7 1.6 0.3
Mar 3.0 1.7 0.8 0.2
Apr 0.7 0.3 0.2 0.1
May 0.1 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 0.1 0.0 0.0
Nov 1.5 0.7 0.3 0.1
Dec 5.2 2.3 1.1 0.3
Annual 21.7 11.3 6.1 1.2

Growing Season Summary

Station: 111497 CHICAGO BOTANICAL GARDEN, 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 5 16 84 230 545 820 1024 983 716 399 110 19 4894
45 1 5 46 135 394 670 869 828 566 263 53 8 3798
50 0 1 24 73 261 520 714 673 421 154 22 3 2841
55 0 0 11 39 159 378 559 518 285 78 7 1 2020
60 0 0 5 19 88 249 405 365 171 30 1 0 1327
50** 3 9 52 126 309 518 687 658 439 224 50 10 3052

**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 4/25 4/09 4/13 5/16 5/27 10/12 9/22 9/30 11/01 11/06
30 4/22 3/28 4/07 4/30 5/07 10/22 9/23 10/03 11/08 11/12
28 4/11 3/25 4/03 4/24 4/28 10/24 10/08 10/10 11/17 11/20
24 4/06 3/12 3/18 4/19 4/23 11/12 10/19 11/01 11/29 12/05
20 3/21 2/17 3/10 4/10 4/10 11/21 11/03 11/08 12/09 12/22
16 3/16 2/17 2/19 4/02 4/07 11/24 11/03 11/12 12/20 12/24

Length of Growing Season (Days)

Derived from 1981-2000 Averages

Temp °F Median Shortest 10% 90% Longest
32 170 150 151 180 201
30 188 152 160 211 214
28 197 172 181 221 225
24 219 197 202 247 248
20 247 216 218 274 283
16 267 221 225 283 285

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