OneTaskBy Tim King · Updated
US Frost Dates
Searchable by Town, Airport or State, With 1-in-10 Risk Dates and Growing Season
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How the US Frost Dates works
This table of US frost dates gives the typical last spring frost and first fall frost for 6,948 NOAA weather stations, from the official 1991–2020 climate normals. Search your town, the nearest airport or a two-letter state code to find when it is safe to plant out tender crops and how long your growing season runs.
How to read the frost dates table
A frost here means the air temperature at the station dropped to 32 °F (0 °C) or below. The median dates are the ones most planting calendars quote: in half of years the last spring frost comes before that date, and in half after. The 1-in-10 columns are the cautious choice — the last spring frost comes later than that date in only one year in ten, and the first fall frost comes earlier than that date in only one year in ten.
Picking the right station
Stations are named the way NOAA names them, so an airport reads as "Ap" and a distance such as "2 N" means two miles north of the town. Pick the station closest to you in both distance and height; valleys and low ground collect cold air and often frost a week or two later in spring than a hilltop station nearby. Stations that almost never freeze, such as much of southern Florida and Hawaii, have no freeze normal and are not listed.
Growing season length
The frost-free days column is the median number of days between the last spring and first fall 32 °F freeze. Compare it with the days to maturity on a seed packet to see whether a crop will ripen outdoors, or whether it needs starting indoors or a cold frame to stretch the season.
FAQ
When should I plant after the last frost date?
Frost-tender crops such as tomatoes, peppers, squash and basil go out after the median last frost date, and gardeners who cannot risk a loss wait until the 1-in-10 date. Hardy crops such as peas, spinach and onions can go in two to four weeks before the median date.
Where do these frost dates come from?
They are the freeze-probability normals in the NOAA National Centers for Environmental Information 1991–2020 U.S. Climate Normals, the official 30-year averages published every decade. As a US Government work they are in the public domain and free to reuse.
Why is my town missing from the frost dates list?
Only stations with enough years of daily minimum temperatures get a freeze normal, so small towns without a long-running station are absent. Search the county seat, the nearest airport or a town a few miles away at a similar elevation instead; the dates rarely differ by more than a few days.
Can I download the US frost dates?
Yes. The CSV and JSON buttons give you all 6,948 stations with both frost dates at the median and 1-in-10 risk levels, the frost-free season length and the NOAA station ID, so you can join them to other climate data.
See also: all Everyday Data tools, Tech Data.
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