Last Frost Date by Zip Code

What are frost dates and why do they matter?

Frost dates are the statistical average dates when temperatures drop to 32°F in spring (last frost) and fall (first frost) at a given location. They are the foundation of US vegetable garden planning — transplanting tender crops before the last spring frost or leaving them out past the first fall frost costs you the harvest.

Frost dates come from NOAA weather station data collected over 30 years. The dates you see in references like the Old Farmer’s Almanac represent the day when 50% of historical years recorded a frost. That means on average, half of all springs have frost after that date and half do not.

For crops that die at 32°F — tomatoes, peppers, basil, cucumbers, squash, and beans — a single frost event eliminates the planting. For this reason, most experienced US gardeners plant tender vegetables 2–3 weeks after the average last frost date, not on the date itself.

Frost dates and USDA hardiness zones are separate but related data. Your hardiness zone tells you what plants survive your winters; your frost dates tell you when the growing season starts and ends each year. Both pieces of information are necessary for garden planning. For zone context, see the planting zones guide.

Average last spring frost dates by USDA zone

Note: These are regional averages. Your specific location may differ by 1–3 weeks from the zone average. Local elevation, proximity to large water bodies, and urban heat island effects all shift frost dates significantly.

Last frost dates for major US cities

City-level data is useful for orientation but your specific neighborhood may differ significantly. Urban areas run 2–5°F warmer than surrounding rural areas (urban heat island effect). Valley floors run colder than hillsides (cold air drainage). North-facing slopes in hilly terrain can experience frost 2–3 weeks later than south-facing slopes 200 feet away.

How to find your exact last frost date

The most accurate frost date lookup for your specific location uses zip code or address, not just zone or city.

Three reliable US sources:

1. Old Farmer’s Almanac Frost Chart URL: almanac.com/gardening/frostdates Covers 3,200+ US stations. Enter your zip code to get both spring and fall frost dates with probability breakdowns (10%, 50%, and 90% probability).

2. NOAA’s 1981–2010 Climate Normals Available through NOAA’s National Centers for Environmental Information. Detailed station-level data.

3. Cooperative Extension Services Each state’s land-grant university publishes local frost date maps. Virginia Cooperative Extension, Penn State Extension, and Texas A&M AgriLife Extension are among the most detailed.

The probability breakdown matters more than the single date. The Old Farmer’s Almanac reports three numbers:

• 10% probability date: Very safe — only 1 in 10 years has frost after this date. Use for cold-sensitive crops you really cannot lose.
• 50% probability date: The “average” date most references quote.
• 90% probability date: Half of all years have frost before this date — risky territory for tender crops.

For tomatoes and peppers, experienced US gardeners typically target the 10% probability date or 2–3 weeks past the 50% date.

Seed starting calendar based on last frost date

One of the most practical uses of frost dates is backward-planning your seed starting schedule.

Starting seeds too early produces tall, leggy transplants that struggle when moved outdoors. Starting too late wastes your head start advantage. The goal is to have transplants at the ideal size exactly at transplant time.

Cucumbers and squash are often direct-sown after last frost rather than started indoors — they grow quickly and do not transplant as well as solanums (tomatoes, peppers). Two to three weeks indoors is the maximum before they become root-bound.

Full tomato growing guidance — including transplant timing by zone — is in the how to grow tomatoes guide.

Direct sow dates relative to last frost

Some crops are planted directly in the garden, not started indoors. Their timing relative to last frost:

Cold-hardy crops can go in 4–6 weeks before last frost because they tolerate temperatures as low as 25°F. Light frosts (28–32°F) do not damage them. Hard frosts (below 28°F) may.

How to use fall frost dates

Your first fall frost date is the deadline for:

Harvesting tender crops: Tomatoes, peppers, eggplant, cucumbers, squash, and basil die at first frost. Harvest all mature and nearly mature fruit 1–2 days before the predicted freeze. Green tomatoes ripen in a warm indoor location if they have reached full size.

Moving tender container plants indoors: Bring in frost-sensitive potted plants — citrus, figs, tropical ornamentals — before the first predicted freeze. Many of these recover from one frost but not two.

Planting fall and winter vegetables: Count backward from first fall frost to find the latest date for planting cold-season crops. Broccoli needs 60–70 days to maturity, so plant at least 70 days before first fall frost.

The how to start a vegetable garden guide covers both spring and fall planting windows in detail.

Why frost dates sometimes miss

Frost dates are statistical averages, not predictions. Several real-world factors make your garden’s frost timing different from the recorded average.

Elevation: Cold air is denser and sinks to low points. Gardens in valley floors, near creeks, or in topographic depressions experience frost 2–4°F colder than gardens on slopes at the same elevation. A hillside garden may never frost on a night when a creek-bottom garden nearby gets frozen solid.

Urban heat island: City gardens run consistently warmer than surrounding rural areas — often 2–5°F warmer overnight. Chicago’s lakefront urban core has a noticeably different frost profile than suburban Chicago even within the same zip code.

Water body proximity: Large lakes and rivers moderate temperatures. The Great Lakes extend the frost-free season on their eastern and southern shores by 2–4 weeks compared to inland areas at the same latitude.

Slope aspect: South-facing slopes receive more sun and stay warmer. North-facing slopes trap cold air and frost later in spring. The practical difference in a hilly garden can be 1–2 weeks between facing slopes.

Microclimates from structures: South-facing walls of houses absorb heat and radiate it at night. A bed against a south-facing brick wall may have a frost date 2–3 weeks earlier than an open garden 30 feet away.

Use recorded frost dates as a starting point. Track your own garden’s actual frost events for 2–3 seasons to calibrate. For tracking and zone context, see the planting zones guide.

Protecting plants around frost dates

When late frost threatens after you have transplanted tender crops, four protection methods work in US gardens:

Row covers (Reemay/floating row cover): 2°F to 8°F of frost protection depending on weight. Lightweight (0.5 oz/sq yd) provides 2–4°F; heavy (1.5–2 oz/sq yd) provides 6–8°F. Most versatile option for US home gardens — drape directly over plants, secure edges, remove during warm days for pollination access.

Cold frames: A box with a clear lid (glass or polycarbonate) creates a microclimate 10–20°F warmer than outside air. Extends the season by 4–6 weeks in both directions.

Water walls (Wall-O-Water): Water-filled tubes arranged around a single plant. Holds heat released slowly overnight. Provides protection to 16°F. Commonly used for early tomato transplanting in Zone 5.

Cloches: Individual plant covers of glass, plastic, or waxed paper. Useful for isolated plants but impractical at scale.

For raised bed season extension options, see the raised bed garden plans guide.

Frost date planning for herbs

Herbs have widely varying frost tolerance. Basil dies at first frost — it is more cold-sensitive than tomatoes. Parsley, cilantro, and chives tolerate light frost (28–32°F). Rosemary and thyme are perennial to Zone 6 and survive hard freezes.

For indoor herb growing that extends past the frost date season, see the how to grow herbs indoors guide.

Finding frost probability data, not just averages

For US gardens with real cold-sensitive crops at stake, the 50% probability date is not sufficient. Use the 10% probability date from the Old Farmer’s Almanac frost tool for any crop you cannot replace easily.

Practical planning rule by crop value:

The Old Farmer’s Almanac frost chart and the USDA Plant Hardiness Zone Map are the two most authoritative US references for frost date and hardiness planning. Neither charges for access. Both are updated regularly with new station data.

Full-sun perennials and frost dates

Frost date knowledge also applies to perennial garden planning. Many full sun perennials require particular planting windows — spring-planted perennials need to establish roots before summer heat in Zone 7 and warmer; fall-planted perennials establish better in Zones 5–7 where springs are short. Knowing your frost dates helps you pick the right planting window and avoid losing expensive perennial plantings to poor timing.