Free Tool
Enter your ZIP and get your own calendar — what to start indoors this week, what to direct sow, and the last safe date to plant each crop and still beat first frost. Built on NOAA frost normals for 33,000+ ZIP codes.
Your ZIP is only used in your browser — nothing is sent anywhere, and the calendar is remembered on this device.
Every date below is calculated from your frost dates. "Last safe sow" is the last day you can direct sow and still get a harvest before frost ends the season.
| Crop | Start indoors | Transplant out | Direct sow | Last safe sow | Frost |
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These crops come in all at once, so sowing a small batch every few weeks beats one big planting. Dates already past this season are dimmed; the next one is highlighted.
Heads up: the seed links are Amazon affiliate links. If you buy through them it doesn't cost you anything extra, and it helps keep these guides coming. They point at category searches rather than a single product, so you can pick the varieties and day-lengths that suit your season.
Your two frost dates come from the NOAA 1991–2020 US Climate Normals — specifically the dates with a 50% probability of the last spring and first fall 32°F freeze. Every ZIP code centroid (US Census 2023 ZCTA gazetteer) is matched to the three nearest reporting stations and blended by distance, so the answer reflects your area rather than the nearest big airport. The card above tells you how far away the closest station is; under about 15 miles the number is solid, and much beyond that you should treat it as a regional estimate.
A 50% probability is exactly what it sounds like. In half of years the last spring freeze lands later than that date. If you're planting something you can't replace, wait a week or two past it, or be ready to cover.
Indoor sowing windows come from the University of Minnesota Extension's seed starting guide — tomatoes 5–6 weeks before last frost, peppers and eggplant 9, brassicas 10–11, onions and leeks 14–15. Outdoor timings follow Colorado State University Extension's raised-bed planting guide, whose schedule is built around a May 15 last frost, so its dates convert cleanly into weeks before or after your own.
Counting back from first frost uses the standard extension formula: days to maturity, plus a two-week fall factor because a crop sown in August grows more slowly as days shorten, plus another two weeks for crops that frost kills outright rather than merely checks. Days to maturity and frost tolerance come from the University of Minnesota Extension's midsummer planting guide. Hardy crops — kale, collards, cabbage, brussels sprouts — are counted to first frost rather than two weeks before it, because a light freeze improves them.
Days to maturity varies by variety, sometimes by three weeks or more, and the packet in your hand beats any general figure. Where a range exists this tool uses the slow end, so its last-safe dates are conservative on purpose.
Elevation, your south-facing wall, the cold hollow at the bottom of the yard, and soil temperature — which is what actually governs germination in early spring. Frost dates are a planning tool, not a thermometer. Pair this with our raised bed planner for spacing and layout once you know what you're sowing.