Growing season calculator
How many frost-free days do you get, and will the pumpkin you plant this week ripen before they run out? Enter your ZIP, pick a crop and a planting day.
185 frost-free days
For Columbus, Ohio (example).
Your frost-free window runs from about Apr 20 to Oct 24 in a typical year. In a bad year (last frost at the 10% date, first frost at the 10% date) it shrinks to about 159 days.
Will it ripen before frost?
Ready around September 27.
Yes, with about 27 days to spare before the average first frost.
What "growing season" means for a gardener
Weather services define the growing season as the frost-free period: the days between the last 32°F night in spring and the first in fall. NOAA's normals report the length that is exceeded in half of years, which is the figure Seasonwise shows.
For vegetables the useful season is a little different for each crop. Frost-hardy kale and carrots grow for weeks outside the frost-free window. Tomatoes, peppers and melons also need warmth, not just an absence of frost: they barely grow when nights drop below 50°F, so in a cool coastal climate the effective season is shorter than the frost-free days suggest.
Reading days to maturity
Seed catalogs count days to maturity from the day a seedling is transplanted for crops usually started indoors (tomatoes, peppers, brassicas) and from sowing for direct-sown crops (beans, squash, corn). A "75-day" tomato therefore spends another six to eight weeks indoors before that clock starts.
Planting by the Moon?
Farmers' almanacs still suggest sowing by lunar phase. Controlled trials haven't shown a reliable effect on yield, so let frost dates and soil temperature lead. The Moon itself is still worth understanding, and ahaboo has a narrated, hands-on explainer showing why it waxes and wanes.
Growing season FAQ
How long is my growing season?
Your growing season is usually measured as the number of days between the average last spring frost and the average first fall frost (32°F). Enter your ZIP code to get the figure from NOAA's 1991–2020 climate normals for your nearest station.
How do I know if a vegetable will ripen before frost?
Add the variety's days to maturity to its planting date. For transplants, the count starts on transplant day; for direct-sown crops, on sowing day. If the result falls before your first frost date, with a week or two to spare for cool autumn weather, it should ripen.
Why do crops take longer than the days to maturity on the packet?
Days to maturity assume warm, long days. In spring and fall, growth slows. Extension services commonly suggest adding 1–2 weeks for fall crops, which is sometimes called the "short day factor".
How can I extend a short growing season?
Start warm-season crops indoors, choose early varieties, warm the soil with black plastic, and protect plants with row cover, cold frames or low tunnels, which can add several weeks at each end of the season.