Frost-Free Days & Growing Season Length by Zip Code Map
Your frost-free season is the window you actually have to grow in. It is the stretch between your last spring frost and your first fall frost — the number of days warm-season crops have to sprout, grow, and ripen. This map gives you the average frost-free days, also called growing season length, for your ZIP code.
How to use the map: enter your ZIP code in the search box below to see your average number of frost-free days. Compare that number to a crop’s days to maturity to know whether it can finish in your season.
Frost-Free Season
Average frost-free days
Monthly Rainfall
Frost-free days on this map are calculated from a 30-year average of climate data from 1991 to 2020, which gives you a stable baseline rather than one unusual year. Treat the number as a typical season; a year with an early fall frost or late spring frost runs shorter. Frost pockets and high, exposed sites have shorter seasons than sheltered, urban, or south-facing ground.
Frost-free days are simply the span between your last spring frost and first fall frost. For the full climate picture, pair them with your USDA hardiness zone and growing degree days.
What Are Frost-Free Days?
Frost-free days — also called the growing season length — is the average number of days between the last frost of spring and the first frost of fall. It is the practical length of your warm-season growing window, and it sets the outer limit on what you have time to grow from spring to fall.
How to Use Your Growing Season Length
- Check days to maturity. Compare a crop or variety’s days to maturity against your frost-free days; if maturity is close to or longer than your season, you’ll need a head start or a faster variety.
- Choose short-season varieties where needed. Cool, short-season areas favor quick-maturing cultivars; long-season areas can grow nearly anything and squeeze in succession crops.
- Get a head start. Starting seeds indoors or buying transplants effectively lengthens a short season by moving early growth before the last frost.
- Stretch the shoulders. Row cover, cold frames, and tunnels can add a few weeks at each end for borderline crops.
Frost-Free Days by Region
Growing season length swings widely across the country. The far north, the Mountain West, and high elevations may see only 90 to 120 frost-free days, while the Deep South and mild coasts enjoy 250 days or more — and frost-free climates like South Florida and coastal California can grow year-round. Elevation and cold-air drainage can shorten the season sharply even within a single county, which is why a ZIP-level number beats a regional guess.
How Accurate Is a Frost-Free Days Map?
It is a dependable average built from your local frost dates, but because it depends on two variable events — the last spring frost and the first fall frost — the real number swings from year to year. Your exact site can run shorter or longer than the regional figure. Use it to choose varieties and plan, and watch the forecast at each end of the season.
What are frost-free days?
Frost-free days are the average number of days between your last spring frost and your first fall frost — in other words, your growing season length. It is the practical window you have to grow warm-season crops.
How long is my growing season?
Use the map and ZIP lookup above for your average frost-free days. Growing seasons range from around 90 to 120 days in the far north and high elevations to 250 days or more along mild southern coasts.
How do I use growing season length to choose plants?
Compare your frost-free days to a crop’s days to maturity. If the crop needs nearly as many days as — or more than — your season provides, choose a faster variety or start it early indoors.
Can I grow long-season crops in a short season?
Often yes, with help. Starting seeds indoors, buying transplants, choosing short-season varieties, and using row cover or cold frames can all stretch a short frost-free window enough to finish a longer crop.
How accurate is a frost-free days map?
It is a solid 30-year average, but it depends on two variable frost dates, so the real number shifts year to year and by site. Use it for variety selection and planning, and confirm with the forecast at each end of the season.
Sources and Further Reading
- NOAA 1991–2020 U.S. Climate Normals, freeze/frost dates — the base data behind these frost-free day counts.
- NOAA growing-season-length and probability-of-freeze data — methodology for frost-free periods.
Next step: match your season length to plants that fit. Check your last frost and first frost dates, or use the Plant Finder to match plants to your full climate.