NOAA frost-date interval tool
Growing season length by ZIP Code
Estimate the days between typical last spring and first fall frost dates for your U.S. ZIP Code, using the nearby NOAA station shown with your result.
No account needed. Your ZIP Code is used for this lookup and is not saved in a user database.
What this estimate means
A frost-date interval, not a growing guarantee
The calculator measures the calendar days between a historical last spring freeze date and first fall freeze date. It uses NOAA's 32°F probability dates as a consistent planning boundary. Soil temperature, crop needs, microclimate and this year's forecast still determine what can grow outdoors.
Why the table has three intervals
NOAA provides spring and fall dates at separate historical probability levels. The cautious pair uses dates with a 10% freeze risk at each boundary, the middle pair uses 50% dates, and the less cautious pair uses 90% dates. The paired values do not describe the joint probability of the full interval.
Turn the interval into a crop plan
Use the interval as a first screen, then check a seed packet's days to maturity and the crop's temperature requirements. For crops started indoors, count backward from a suitable outdoor planting date.
Sources and matching limits
ZIP Codes are approximated by 2025 Census ZCTA centers and matched to a nearby qualifying NOAA station from the 1991-2020 U.S. Climate Normals. The result shows station distance and record completeness so you can judge the estimate.
Sources: 1991-2020 U.S. Climate Normals and 2025 Gazetteer ZCTA National File. Read the matching method.