Frost date calculator
Last spring frost and first fall frost for your exact location, worked out from 30 years of nightly lows, not a table of airports.
How to use your frost dates
- Hardy crops (peas, spinach, onions, potatoes): sow or plant 2–6 weeks before the average last frost.
- Half-hardy crops (lettuce, broccoli, carrots): around the last frost date.
- Tender crops (tomatoes, peppers, beans, squash, basil): after the “safe” date, once soil has warmed.
- Fall crops: count back from the first fall frost by the days to maturity on the seed packet, plus about two weeks because growth slows as days shorten.
For crop-by-crop dates, the planting calendar turns these numbers into sowing windows for 16 vegetables.
Questions gardeners ask
What is the average last frost date?
It is the date after which, in half of past springs, there was no further frost of 32°F. So planting on the average date still carries roughly a 50% chance of another frost. For tender plants, gardeners use the 10% date instead, which PlantWise shows as “safe”.
Where does the frost data come from?
Daily minimum temperatures for 1995–2024 from the ERA5 reanalysis (ECMWF’s Copernicus Climate Change Service), served by Open-Meteo. We compute the dates for your exact location, not the nearest airport.
Why is my forecast frost different from these dates?
These are climate averages. A forecast describes the next few days. Always check the forecast before planting out, and cover tender plants if a frost is predicted.
What is a hard freeze?
Usually 28°F or below for several hours. A light frost at 32°F kills tender plants such as tomatoes and basil; a hard freeze also damages hardy crops and ends the season for most vegetables.
Why can my garden get frost when the weather station says 34°F?
Air temperature is measured about 6 feet above the ground. On clear, still nights, cold air pools at ground level and in low spots, so plants can frost when the thermometer reads a few degrees above freezing.