We tend to remember those Halloweens with bad weather. Slogging through rain or snow in costumes with trick-or-treat bags is tough. But according to Dr. Ed Hopkins of the Wisconsin State Climatology Office, in the last 30 years (1981-2010), Madison has had only 10 Halloween days when measurable precipitation (0.01 inches or greater) fell, which translates to a probability of 33 percent that rain falls on that date. Halloween 1985 was memorable in Madison for its 1.05 inches of rain. The most precipitation for Oct. 31 was 1.21 inches in 1960.
Of greater interest is the amount of rain that falls during the late afternoon and early evening when most trick-or-treaters are making their rounds. In 1979, 0.31 inches of rain fell from about 4 p.m. until 7 p.m., of which nearly a quarter of an inch fell during the hour between 4 p.m. and 5 p.m. Since 1996, little significant rain has fallen during the afternoon and evening.
Air temperatures have varied widely during the late afternoon and early evening hours, including one Halloween low of 28 degrees in 1996. Over the last decade, Madison trick-or-treaters have experienced only two holidays with the temperature near freezing. While trace amounts of snow fell in 1993 and 1995, no measurable snow (0.1 inches or more) has fallen on Halloween since records have been kept at the Dane County Regional Airport.