National Weather Service United States Department of Commerce

...NWS Gray will conduct an experiment this fall to improve services related to the Frost/Freeze Program...  

 

The National Weather Service’s (NWS) Frost/Freeze Program consists of issuing Frost Advisories, Freeze Warnings or Hard Freeze Warnings when cold temperatures threaten tender vegetation and crops during the climatological growing season. The growing season is defined by the period of time between the median date of the last Spring Freeze and the median date of the first Fall Freeze. 

Currently, the ending of the issuance of Frost/Freeze headlines for a season in a weather forecast zone is based on the first occurrence of a freeze, or two weeks after the median first Fall freeze date when no freeze occurs. This approach was confusing to many users as meteorological conditions often led to a patchwork approach of ending the growing season across multiple weather forecast zones and NWS offices.  The patchwork approach would keep certain forecast zones in the growing season, while the adjacent forecast zone growing season would have ended.

The Northern New England NWS forecast offices (Burlington VT/Caribou ME/Albany NY) and the NWS Gray ME office will conduct an experimental program service during the fall of 2022. The purpose of this experimental program is to streamline the Frost/Freeze program for simplified customer usability.  

The end of the seasonal Frost/Freeze program will be determined by the climatological 75-90th percentile of the median first Fall freeze date.  On average this date is 10 days after the median first Fall freeze.  This means that these NWS offices will use a fixed date for the climatologically defined areas, based on 30-Year temperature averages, to end the growing season. 

During the defined growing season, NWS Gray will issue frost/freeze headlines as needed. Once the 75-90 percentile of the median end date of the climatologically defined growing season is reached, frost/freeze headlines will no longer be issued for that climatological area as frost and freeze conditions are expected.  Note: this means there could be multiple freeze warnings issued towards the end of the season for the same forecast zone.   

The following are the climatologically defined areas and their respective 75-90th percentile of a first fall freeze, for which frost/freeze headlines will no longer be issued.

Location

Frost / Freeze End Date

Coos County NH & Western Maine Mountains October 1st
Maine Foothills, White Mountains, CT River Valley, Monadnock Region, NH Lakes Region and Merrimack River Valley October 11th
NH Seacoast, Maine Midcoast, York, Cumberland, Androscoggin & Kennebec Counties October 21st


If you have any questions or comments on this experiment, please reach out to Donald Dumont, Warning Coordination Meteorologist at donald.dumont@noaa.gov or call 207-688-3216.

FrostFreeze