After some controversy over just how bad the weather gets in Austin, I decided to go pick up some actual historical data from the NOAA web site.
First, the monthly averages, in turn averaged for 1931-2000:
City
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Austin TX
52.1
55.7
62.2
69.4
75.9
81.6
84.1
84.1
79.3
71.2
61.0
54.3
Boston MA
24.7
26.4
35.2
45.9
57.0
65.9
71.0
69.1
61.1
50.7
40.5
29.0
Minneapolis MN
9.4
15.1
27.4
43.4
56.8
66.5
71.3
68.7
58.9
47.4
29.7
15.6
Of course, averages don’t tell the whole story—so I took the last ten years of monthly maximum temperatures, [...]