Frost dates explained, and how to use them
Last reviewed September 2026 · written from public-domain USDA/NOAA data and Cooperative Extension references — see how we source data
Almost every planting decision in a temperate garden is counted forwards or backwards from two dates: the average last frost in spring and the average first frost in fall. Get those roughly right and the rest of the calendar falls into place.
What the dates mean
A frost date is a probability, not a deadline. The commonly quoted "average last frost" is usually the date after which there is only a 50% chance of another 32°F night. There is still meaningful risk for a week or two beyond it.
Conservative gardeners use the 10% date (about two weeks later in spring) for tender crops they cannot afford to lose, and the 50% date for hardy crops and for succession sowings they can replace.
Finding yours
NOAA publishes freeze/frost "normals" for thousands of US weather stations. Your county Cooperative Extension office also publishes local dates and usually knows the microclimate quirks of the area.
This site's frost date finder uses NOAA-derived state averages as a starting point. Because a state can span a month of variation, entering your own dates from a nearby station is worth the two minutes.
How planting dates are built from them
Start seeds indoors: last frost minus the crop head-start (6–8 weeks for tomatoes, 8–10 for peppers and onions, 3 for cucurbits).
Direct sow hardy crops: several weeks before the last frost, as soon as soil is workable. Direct sow or transplant tender crops: one to two weeks after the last frost, once soil is warm.
Fall crops: first frost minus days to maturity minus a short buffer, working backwards so the crop matures before or just after frost depending on how hardy it is.
Adjusting for your garden
A south-facing slope, a fenced urban yard or a spot near a heated wall can run a week or two ahead of the official date. A frost pocket at the bottom of a hill runs behind it. Keep notes for a season or two and shift your personal dates accordingly.