Last Frost Date and First Frost Date by Zone: How to Find Yours

Your last frost date is the average date of the final 32°F night in spring, and your first frost date is the average date of the first 32°F night in fall. They are calculated from NOAA climate records for weather stations near you, not from your USDA hardiness zone. Zones give you a rough idea, though: in zone 5 the last spring frost usually falls in late April to mid-May, while in zone 8 it is often mid-March to early April.

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Hardiness zones are not frost dates

The 2023 USDA Plant Hardiness Zone Map divides the country by average annual extreme minimum winter temperature, based on 1991-2020 data. Each zone covers a 10°F range, split into “a” and “b” half zones of 5°F. Zone 6, for example, means the coldest night of a typical winter falls between -10°F and 0°F.

That number tells you which perennials, fruit trees and overwintering crops will survive. It does not tell you when spring’s last frost arrives. Frost timing depends on latitude, elevation, distance from large bodies of water and local terrain. A coastal town and an inland valley can share a zone and still have last frost dates three or four weeks apart.

So use the zone table below as a starting point, then look up the actual dates for your location.

How frost dates are calculated

NOAA’s National Centers for Environmental Information publishes U.S. Climate Normals, 30-year averages currently based on 1991-2020. For thousands of weather stations, the normals include the probability of reaching 36°F, 32°F, 28°F and lower on each day of the year.

From those records come the frost dates gardeners use:

• Last spring frost (50%): the date after which there is a 50% chance of another 32°F night. NOAA’s Climate.gov describes it as the point when the chance of freezing temperatures for the rest of spring drops below 50%.
• Last spring frost (10%): a later, safer date. Only about 1 year in 10 brings a frost after it.
• First fall frost (50% and 10%): the same idea in reverse. The 10% date for fall is earlier, the date before which a frost happens only about 1 year in 10.

Some sources also list a 28°F date, sometimes called the killing freeze, which matters for hardy crops like kale and cabbage. Light frost and hard freeze are different events, and our guide to how to cover plants for frost explains what each one does to your garden.

How to find your frost dates by ZIP code

There is no single official “frost dates by ZIP code” list, because the data come from weather stations, not postal codes. The good news is that free public tools make it easy to find the nearest station.

1. Start with NOAA. Climate.gov has an interactive map of the average date of the last spring freeze, built on the 1991-2020 normals. Zoom to your area and click the station closest to you.
2. Check your National Weather Service office. Many local NWS offices post frost and freeze tables for the cities they cover, often with median, early and late dates. Search “frost freeze dates” plus your NWS office or city.
3. Ask your state extension service. Land-grant universities and county extension offices publish planting calendars with local frost dates. Some state climate offices offer lookup tools too.
4. Pick the right station. Choose one with a similar elevation and setting to your garden. A station on a hilltop or at a downtown airport may run warmer than a rural valley a few miles away.
5. Write both numbers down. Note the 50% and 10% dates for spring and fall, and keep them with your garden notes.

Average last frost and first frost dates by zone

The table below shows typical, approximate ranges for each zone across the continental U.S. Because zones and frost dates measure different things, the real dates for your town may fall outside these ranges. Always confirm with local data or your extension office, because microclimates vary.

In zones 8-10, the calendar flips. Summer heat, not frost, is often the main limit, and fall through spring is prime time for lettuce, broccoli, carrots and other cool-season crops.

When is the first frost?

For most of the northern half of the country (zones 3-5), the first fall frost arrives sometime in September or early October. In zones 6-7, which cover much of the Mid-Atlantic, Ohio Valley and lower Midwest, expect it in October or early November. The Deep South, Gulf Coast and Southwest deserts (zones 8-9) typically see their first frost from November into December, and parts of zone 10 may go years without one.

Weather forecasts beat averages once the season arrives. When a frost advisory or freeze warning appears in your 7-day forecast, act on it, even if it comes two weeks ahead of your average date.

How to use frost dates to plan your garden

Frost dates work as anchor points. Almost every seed packet and planting guide gives timing in “weeks before” or “weeks after” the last frost, so once you know your date, the rest is simple counting.

Starting seeds indoors

Count backward from the date you plan to transplant. University of Minnesota Extension suggests keeping tomatoes indoors about 5-6 weeks and peppers and eggplant about 9 weeks before they move outside, while onions and leeks need 14-15 weeks. Cabbage-family crops are hardy enough to set out a couple of weeks before the last frost.

Example (zone 6, last frost around April 20):

• Plan to transplant tomatoes and peppers around May 1-10, once nights stay above 50°F.
• Start peppers and eggplant indoors in early March.
• Start tomatoes indoors in late March.
• Start onions from seed in mid to late January.
• Harden off all transplants for 7-14 days before planting out.

Planting tender crops outdoors

Beans, squash, cucumbers and corn go in after the last frost, once the soil warms. Waiting one to two weeks past your 50% date, or until your 10% date, lowers the frost risk a lot and gives seeds warmer soil to sprout in.

Scheduling fall crops

For fall planting, count backward from your first frost. A method shared by Virginia Cooperative Extension master gardeners adds two buffers to the days to maturity on the seed packet: about 14 days as a “fall factor” for slower growth in shorter, cooler days, plus another 14 days for frost-tender crops so they finish before the cold.

Example (zone 6, first frost around October 20):

• Bush beans, 55 days: 55 + 14 + 14 = 83 days. Count back 83 days from October 20 and you get about July 29 as your last sowing date.
• Spinach, 45 days: spinach handles frost, so skip the frost-tender buffer. 45 + 14 = 59 days, or a sowing date around August 22.

Hardy crops such as kale, spinach and carrots can keep growing past the first frost, especially under row cover or in a cold frame. For full planting lists, see our fall vegetable garden guide and what to plant in October.

Frost dates are shifting

NOAA updates the normals every ten years, and the 1991-2020 set replaced the 1981-2010 averages, so an old frost-date chart in a garden book may be out of date. The 2023 hardiness map, built on the same 30-year period, moved about half of the country into a warmer half zone compared with the 2012 map. Even so, late frosts still happen in warm springs, and one cold night can undo weeks of work. Use the averages to plan, then follow the forecast.

Common mistakes to avoid

• Using your hardiness zone as if it were a frost date.
• Treating the 50% last frost date as a safe planting date for tomatoes and peppers.
• Picking a weather station at a very different elevation from your garden.
• Starting tomatoes indoors too early, which leaves leggy, root-bound plants by planting time.
• Forgetting the fall factor, so fall crops are still maturing when cold weather stalls them.
• Ignoring the forecast because “it’s too early for frost.”

FAQ

Keep reading

• Vegetable Planting Calendar: When to Plant Every Crop, Any Zone
• USDA Hardiness Zones: What Zone Am I In? (2023 Map Explained)
• When to Start Seeds Indoors: Seed Starting Calendar by Crop and Zone

Sources

• Interactive Map: Average Date of Last Spring Freeze – NOAA Climate.gov
• U.S. Climate Normals – NOAA National Centers for Environmental Information
• USDA Plant Hardiness Zone Map (2023) – USDA Agricultural Research Service
• Frost and Freeze Maps – NOAA National Weather Service Raleigh
• Starting Seeds Indoors – University of Minnesota Extension
• Planning the Fall Vegetable Garden – Piedmont Master Gardeners, Virginia Cooperative Extension