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Last & First Frost Date Calculator — By ZIP Code
Enter your ZIP code to see the typical last spring frost, first fall frost, and average growing season length for your exact location, calculated from real historical weather.
Your numbers
Result
Enter your ZIP code, then tap Calculate.
How it's calculated
For each year of available history, the last spring frost is the latest date in January–June with a low temperature at or below your chosen threshold, and the first fall frost is the earliest date in July–December meeting the same threshold. Those dates are averaged across every year of data available for your location to give a typical date, not a single year's outlier.
Growing season length is simply the average number of days between the last spring frost and first fall frost each year.
Based on real historical daily lows for your exact coordinates, not a generic USDA hardiness-zone map. The most recent year may not yet have a fall frost date if it hasn't happened yet this year — that year is simply excluded from the fall/season average until it does.
Row Wise tracks planting windows, frost risk and growth stage automatically for your actual field boundary all season — not just a once-off lookup.
Get notified at launch →Frequently asked questions
Why two thresholds — 32°F and 28°F?
32°F is a light/first frost, enough to damage tender plants. 28°F is a harder freeze that kills most annual crops outright. Different crops and decisions call for different thresholds, so you can check both.
How is this different from a hardiness zone map?
Hardiness zone maps group huge regions into one bucket based on average winter minimums. This calculator instead looks up your exact coordinates and pulls real day-by-day historical lows for that specific location, so it reflects your actual local microclimate rather than a regional average.
Why might a recent year be missing from the fall frost average?
If the current year hasn't reached its first fall frost yet, there's nothing to count for that year — it's automatically left out of the fall and growing-season averages until the data catches up.