Author: Mary Knapp

Freeze dates are very important both for agriculture and for urban dwellers. Gardeners are hoping for an extended growing season, and allergy sufferers are hoping for an end to the pollen. On the Kansas climate page – http://climate.k-state.edu/maps/special/freeze/ – we have maps that show the range of average freeze dates across the state, together with the length of the growing season. The earliest recorded freeze – meaning temperatures reached 32 °F or lower-- is September 13th. In western Kansas, that can occur even earlier. For Colby, St. Francis, Tribune, and Cimarron among others, September 3, 1974 marked the earliest freeze on record. On the other hand, those that would like a nice frost to kill the pollen aggravating their allergies might have to wait awhile. The latest date for a first frost for Manhattan is November 10th and that happened in 1998. In Colby, it is October 28th, 2014. Looking at the period of record for Manhattan, the average date for the first frost is October 14th; for Colby it is October 4th. On the mesonet page -- http://mesonet.k-state.edu/weather/freeze/ -- you can monitor the current season. It also has the advantage of tracking the hours of freezing temperatures, as well as allowing you to select different thresholds. A 24 °F freeze that lasts for several hours will be much more damaging than a freeze that is at 32 °F for a few minutes.

Frost (public domain)

Mary Knapp, Weather Data Library