Frost Date Calculator
Turn your local last spring and first fall frost dates into a growing-season length and a planting schedule for starting seeds indoors and transplanting out. Calculates in your browser.
Growing season
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Show the math
The frost-free season is the gap between your two frost dates:
season = first fall frost − last spring frost
start indoors = last frost − weeks × 7 days
Frost dates are local averages, look yours up from a regional almanac or extension office, then enter them here. Tender crops go out only after the last frost. All math runs locally in your browser.
What this does
A frost date calculator turns your local last spring and first fall frost dates into a growing-season length and a schedule for starting seeds indoors and transplanting out.
How to use it
- Enter your last spring frost date.
- Enter your first fall frost date.
- Set weeks to start seeds early.
- Read the season length and schedule.
How it works
The frost-free window is the days between the two frosts. Many crops start several weeks before the last frost, counted back from that date.
season = first fall frost − last spring frost
Understanding your result
The frost-free window sets what you can grow and when. Count back from the last spring frost to time indoor sowing and hardening off, and watch the first fall frost for harvest deadlines. Frost dates are averages, so a late cold snap is always possible; protect tender plants if one threatens.
Example
A last frost of April 15 and first frost of October 15 gives a 183-day season.
Sources & methodology
Last updated .
Frequently asked questions
Where do I find my frost dates?
Look up the average last spring and first fall frost for your area from a regional almanac or agricultural extension office, then enter them here.
How is the growing season measured?
It is the number of days between your last spring frost and your first fall frost, the frost-free window for tender crops.
When should I start seeds indoors?
Many crops start several weeks before the last frost; the tool counts back the weeks you enter so transplants are ready to go out.
Is anything stored?
No. Everything is calculated locally in your browser.
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