WEATHER TALK: Average First Frost Date Not Really All That Useful(WDAZ-TV) - Cool air masses from up north start dropping into our region with increasing regularity in August, September and October.
By: John Wheeler, WDAZ
(WDAZ-TV) - Cool air masses from up north start dropping into our region with increasing regularity in August, September and October. Eventually, one of these taps into a chunk of very chilly air and puts it right over us on a night with a clear sky and light winds and we end up with frost and rotten tomatoes.
There is a certain amount of randomness to this first frost because it takes the right weather conditions timing out just right with the coolest part of the day. This renders the average first frost date of Sept. 25 somewhat useless. That date actually refers to the average date of the first 32-degree temperature, which has actually varied in history from Aug. 25, 1885, to Oct. 24, 1994.
But scattered frost can happen even when the “official” temperature is above 32 because temperatures are not uniform. Scattered frost occurred on Aug. 20 in 2004 when Fargo’s official low was 34 degrees. However, the weather turned mild in September, and that year’s first official 32-degree temperature did not happen until Oct. 2.