Does the number of below 0 days in winter forecast the summer?

Some common farming folklore is that for every day that the temperature dipped below 0 degrees Fahrenheit in a winter that there is an equal amount of 90 degree days that occur that next summer. There may be some truth to this a certain latitudes where this is in balance, but it appears as though there is little correlation across Chicago and Rockford as most years are either one way or the other. There are a handful of cases where it did matchup perfectly: Chicago-3 times (1924, 1984, and 1994) and Rockford-1 time (1973). For Chicago, most of the years had more 90 degree or higher days than days below 0 in the previous winter (103 out of 137 years with a higher amount of 90 degree days). For Rockford, the data is a bit closer although still leans toward a bias of having more 90 degree or higher days (59 out of 104 years with a higher amount of 90 degree days). This past winter featured 12 days with below zero temperatures at Chicago, while there were 16 at Rockford. Here’s a look at some recent years data as well as a few charts showing the trends.
Year
Chicago
Rockford
 
Days Below Zero
Days Above 90
Days Below Zero
Days Above 90
1989
2
8
10
14
1990
8
10
13
11
1991
6
30
15
29
1992
4
6
5
6
1993
5
11
10
6
1994
17
17
23
9
1995
4
30
9
23
1996
8
10
17
5
1997
11
13
14
9
1998
1
15
2
8
1999
6
22
8
17
2000
3
4
8
4
2001
11
18
21
19
2002
2
23
2
24
2003
3
10
8
14
2004
5
3
8
1
2005
1
26
8
31
2006
3
15
13
10
2007
8
19
14
22
2008
9
6
17
2

 Chicago days difference between below 0 and above 90

Chicago Chart

Rockford difference in days between 0 below and above 90

Rockford Chart



Return to News Archive

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.