As we head further into the Northern Hemisphere’s spring, many people across the country are ready to put winter—and its cold and snow—behind them. But even the spring months can have their cold spells. So when can we expect the cold to really be on its way out? Our “Day of the Last Spring Freeze” map, which is based on climatology, can help answer that question for your area.
Derived from the 1991–2020 U.S. Climate Normals—30-year averages of climatological variables like temperatures—this map shows the most common date range during which areas across the nation can expect to see their temperatures dip to 32°F or below for the last time. The map reveals some interesting regional differences across the country. In the East, the last spring freeze date generally progresses through time as you move northward on the map. However, in the West, the changes are much more complex due to elevation and coastal influences. For additional information and an interactive map, see Climate.gov.
Alaska, Hawaii, and Puerto Rico
Wondering what happened to Alaska, Hawaii, and Puerto Rico? The limited observation network and unique climates of these regions pose distinct issues in calculating the average date of the last spring freeze. In Alaska, many stations have cold summers that lead to a "too cold too compute" condition, preventing reliable mapping of last spring frost. Meanwhile, all of Puerto Rico and all but the highest elevations of the state of Hawaii fall into the “too warm to compute” category, meaning that they very rarely or never see freezing temperatures.
New Ag Normals for 1991-2020 have been produced by NCEI that include the chances of freezing on any given day, or for reaching some other cold threshold important for certain crops or pests. The normal length of the growing season and its first freeze date in the fall are also available, along with the expected growing degree days at any climate station. Ag Normals can help farmers determine when they’re most likely to see their last spring freeze, allowing them to mitigate some risks to crop vulnerability. Additionally, the Ag Normals can help determine where pests are likely to overwinter. Plant nurseries can use these Normals to help determine where and when to advertise plants and seeds to customers in a specific area.
While this map shows the average timeframe of the last spring freeze across the United States, this year’s actual conditions may vary widely based on weather patterns. For prediction of your actual local daily temperature, and to see how it matches up with the Climate Normals, check your local forecast on Weather.gov.