When Is the Last Frost (US Guide)

What the last frost date means — and what it does not

The last frost date is the average date of the final 32°F temperature in spring, calculated from 30 years of historical weather data. It carries a 50% probability — meaning frost is equally likely to occur before or after that date in any given year.

This statistical reality surprises many new gardeners who treat the last frost date as a hard deadline. It is not. In any given spring, there is a 50% chance of frost after the average date. The 10% probability date — available from many frost date tools — gives you a far safer window for your most cold-sensitive plants.

The distinction matters most for frost-sensitive crops: tomatoes, peppers, basil, beans, squash, and eggplant. A single night at 29°F after planting can kill an entire season’s transplants.

For cold-hardy crops — kale, spinach, peas, lettuce, and brassicas — the last frost date is irrelevant as a planting limit. These crops tolerate freezing temperatures and can go in the ground 4–8 weeks before the average last frost.

For zone-specific planting schedules that go beyond frost dates, see last frost date by zip code for the Old Farmer’s Almanac lookup tool and regional planting windows.

Last frost dates by USDA zone

These are approximate average dates for major US regions. Exact dates vary by specific location, elevation, and microclimate.

The “safe for tomatoes” column assumes waiting 2 weeks past the average last frost date and soil temperatures reaching 60°F — the minimum for healthy tomato growth.

These dates shift based on your specific location. Coastal areas are generally milder than inland locations at the same latitude. High-elevation areas in the Rockies, Appalachians, and Sierra Nevada run weeks later than valley locations in the same zone.

How to find your specific frost date

Three reliable sources for US frost dates:

1. Old Farmer’s Almanac (almanac.com/gardening/frostdates): Enter your zip code for spring and fall average dates and the 10%, 50%, and 90% probability thresholds. Most useful for planning.

2. USDA Plant Hardiness Zone Map (planthardiness.ars.usda.gov): Shows your zone but does not give specific frost dates. Use as a starting point, then look up zone-specific data.

3. Local Cooperative Extension Service: Your state’s land-grant university extension provides county-level data. Penn State Extension, Michigan State Extension, and the University of Georgia Extension all publish frost date tables with local weather station data.

The most accurate source is your closest National Weather Service weather station, accessed through weather.gov. These stations often have 50-plus years of frost data for the exact location.

Frost probability dates: the safer planning tool

Most gardeners reference the 50% average but should plant tender crops at the 10% date. The 10% date is typically 2–4 weeks later than the average, depending on zone.

Example for Zone 6b Nashville:

• 90% probability date: April 1
• 50% average last frost: April 15
• 10% probability date: May 10

A gardener who waits until May 10 to plant tomatoes outdoors has only a 10% historical chance of losing plants to a late frost. The 3-week wait from April 15 to May 10 is almost always worth it.

What to plant before the last frost

Frost tolerance varies dramatically between vegetable and flower types. Knowing which plants can handle cold opens up 4–8 extra weeks of spring growing.

Plant 6–8 weeks before last frost (tolerates hard freeze to 25°F):

• Kale, collards, Brussels sprouts
• Onion sets and transplants
• Garlic (fall planted, but spring-transplanting works)
• Spinach, arugula, mache
• Pansies and snapdragons

Plant 4–6 weeks before last frost (tolerates light frost to 28°F):

• Broccoli, cabbage, cauliflower transplants
• Peas (direct sow)
• Beets, carrots, lettuce (direct sow)
• Parsley, cilantro
• Sweet peas (flower)

Plant ON or AFTER last frost date (no frost tolerance):

• Tomatoes, peppers, eggplant
• Cucumbers, squash, melons
• Beans (direct sow)
• Basil
• Annual flowers: marigolds, zinnias, impatiens

For a full schedule of summer vegetables to plant after the last frost, see summer vegetables for timing and variety selection.

Protecting plants from late frosts

Row cover fabric, also called frost cloth or floating row cover, provides 4–8°F of frost protection and extends planting by 2–4 weeks. A single layer of lightweight cover (1.5 oz per square yard) lets in 85% of sunlight while blocking enough heat loss to prevent frost damage in most late-spring cold snaps.

Types of frost protection and their limits:

Row cover works by trapping radiant heat from the soil and plant itself. It is most effective when the soil has stored daytime heat — water soil before a predicted frost night.

Fall frost dates and extending the season

The last spring frost date has a mirror: the first fall frost date, which marks the end of the outdoor growing season for tender crops. The window between them is your frost-free growing season.

Average frost-free growing seasons by zone:

• Zone 3: 80–100 days
• Zone 5: 120–150 days
• Zone 6: 150–180 days
• Zone 7: 180–210 days
• Zone 9: 250–280 days
• Zone 10–11: 365 days (frost-free)

Using fall frost dates for planting: Count backward from your first fall frost to time fall plantings. Broccoli transplants need 60 days to maturity — plant by late July in Zone 6 for a fall harvest before the first fall frost.

For guidance on extending the growing season into fall and winter, see how to winterize garden for techniques that protect crops through the first frosts.

Microclimates: why your garden may differ from the average

South-facing slopes, areas near buildings, raised beds, and urban heat islands all experience last frost dates 1–3 weeks earlier than the regional average. Cold pockets — low spots where cold air settles — run 1–2 weeks later.

Common microclimate effects in US gardens:

Warmer than average:

• South-facing walls and beds (reflected heat)
• Urban and suburban areas (heat island effect)
• Raised beds (drain cold air, warm faster)
• Beds mulched over winter (soil retains heat)

Colder than average:

• Low-lying areas where cold air drains downhill and pools
• North-facing slopes (less direct sun in winter)
• Near large bodies of water that moderate but also cool
• Open, exposed areas with no windbreak

Tracking your own frosts over 3–5 years gives you the most accurate local data. Keep a garden journal noting actual frost dates — after 5 years, you will know your garden’s behavior far better than any regional average.

For understanding the broader planting calendar in your area, see what to plant now by zip code and USDA zones for the foundational zone framework.

Resource: The National Oceanic and Atmospheric Administration (NOAA) provides 30-year climate normals including frost probability data at ncei.noaa.gov — useful for gardeners who want station-specific historical data beyond what zone maps show.