The dates of the last freezing temperatures of the spring and the first freezing temperatures of the fall are of great importance to home gardeners, commercial horticulture, farmers, agribusiness, and others. These dates are sometimes referred to as "last frost" and "first frost".
Accurate long-range forecasts of freeze dates remain beyond the reach of science. Therefore, climatologists rely on past temperature observations to calculate the historical probability of freezing temperatures occurring after (spring) or before (fall) certain dates. Users can use these probabilities to make decisions based on their tolerance for risk.
In freeze date tables for locations noted on the map, a set of probabilities is provided for various temperature thresholds in spring and fall. For example: viewing a "Spring Freeze Dates" table, along the "32" degrees row, and under the ".70" probability column, one might see "4/19". This means that for this location, there is a 70% chance of the temperature falling to 32 degrees F or colder after April 19.
Click on a marker to view a freeze date probability table (PDF document) for that location. Allow pop-ups for this site.
The data tables are provided by the National Climatic Data Center. The 1981-2010 period of record was selected to reflect recent climate trends.