The Farmer's Almanac website, FarmersAlmanac.com, provides an interactive map that lists first frost dates for the United States. The chance of a frost occurring before the listed date is 50 percent. Last frost dates are also provided.
To use the interactive map, users click on a state to reveal a list several cities within the state and their first and last expected frost dates. Frost dates for Hawaii are not included because the majority of the state does not see freezing temperatures.
The dates listed are for a light freeze, which occurs when the temperature is between 29 and 32 degrees Fahrenheit. These temperatures kill tender plants but otherwise have little effect on vegetation.