The occurrence of sub-freezing temperatures inhibits mosquito development and activity. A freeze (28°F) represents relatively severe freezing conditions, whereas a frost (32°F) is generally less detrimental to cold-sensitive biological activity.
The climatological dates of the last spring and first fall frost and freeze are also shown. These are useful for long-range scheduling of mosquito control operations. Shown are the average dates of these occurrences as well as two extremes.
In the spring the 90% and 10% chance dates indicate the probability of experiencing a frost or freeze after a given date. In fall, the dates represent the probability of experiencing a frost or freeze before a given date.