When to Plant Tomatoes: Frost Dates, Soil Temperature and Dates by City

Set tomatoes out once frost is behind you and the ground has warmed. In most of the country the risk of a later frost drops to about 1 in 10 two to three weeks after the median last frost. The soil must also read at least 60°F (16°C), and nights must hold above 50°F (10°C). Start seeds indoors six to eight weeks ahead of that transplant date, not ahead of the frost date.

Two kinds of climate break the pattern. Where springs stay cool, as in the Pacific Northwest and the coastal Northeast, soil and night temperatures set the date long after frost has ended. Where summers are brutal, from the Gulf Coast to the low desert, heat ends fruit set by midsummer, so tomatoes go in as early as frost allows and again for a fall crop.

Tomato planting dates by city

The frost-safe window below opens on the date when the chance of a later frost falls to about 1 in 10 and closes three weeks after that. It is the earliest safe span, not a guarantee, so check the soil thermometer before you plant.

Frost dates are medians from NOAA 1991–2020 climate normals for each city's main weather station, so in half of years the last frost falls later; USDA zone (2023 map) is for that station.

To use the rule where you live, look up your 1-in-10 last-frost date, the date after which a spring frost comes only 1 year in 10. Plant during the three weeks that follow, on the first days your soil reaches 60°F (16°C). If you can only find the median date, add two to three weeks to it before you start counting. The median first frost is your deadline for picking the last fruit and for timing any fall crop.

Four cities need a later date than the frost-safe window, because frost ends there well before the soil and nights warm. In New York, wait until nights stay in the 60s°F (16 to 21°C); the city's last frost can still arrive any time from April 8 to May 1. In Boston, hold off until the soil and daytime air reach 60 to 65°F (16 to 18°C). Around Seattle and the rest of Puget Sound, plant around mid-May. In Sacramento, set transplants out from mid-April into June; the March window is too early there.

Why tomatoes wait for warm soil and warm nights

Tomatoes have no frost tolerance at all. A light frost kills them, 32°F (0°C) injures the leaves and stems, and growth slows to a crawl at 45°F (7°C). They grow best with days of 70 to 80°F (21 to 27°C) and nights of 60 to 70°F (16 to 21°C).

The damage from cold starts well above freezing. Below 50°F (10°C) growth is impaired, and a plant exposed to a run of cold nights can take up to two weeks to start growing normally again. Nights of 50 to 60°F (10 to 16°C) right after transplanting make catfacing more likely: puckered, scarred fruit with deep seams at the blossom end. Nights below 55°F (13°C) also spoil pollen, so the first flowers fall off without setting fruit.

That is why the 60°F (16°C) soil figure matters more than the calendar. On the Colorado Front Range, 55°F (13°C) soil is the accepted floor, and tomatoes prefer 65°F (18°C) or warmer, but 60°F (16°C) is the safe general minimum. Night air should stay above 50°F (10°C), and ideally above 52°F (11°C) with days over 60°F (16°C).

How to tell the soil is ready

Use a soil thermometer rather than the air forecast. Push it in to the depth the root ball will sit and wait for a steady 60°F (16°C) reading on several days in a row. The bed should also be workable: moist soil that crumbles in your hand, not mud that smears. The same thermometer test applies if you grow tomatoes in raised beds; for pots, the guide to tomatoes in containers covers when potting mix is warm enough to plant.

When to start tomato seeds indoors

Sow seeds indoors six to eight weeks before your planned transplant date. In Chicago, for example, a May 1 transplant means sowing between March 6 and March 20. Since most cities' frost-safe windows open 13 to 22 days past the median frost, sowing usually falls three to six weeks before that median date.

A shorter lead time of four to six weeks still gives a good plant. A longer one does not help: seedlings started too early grow leggy and root-bound, are awkward to handle, and do not ripen fruit any sooner.

Sow seed 1/4 to 1/2 inch (6 to 13 mm) deep and keep it at 75 to 85°F (24 to 29°C), on a heat mat if your house runs cool. At 75°F (24°C), seedlings come up in about a week. Once they emerge, grow them on at about 70°F (21°C) under strong light, or they stretch toward the window.

If you buy transplants instead, look for stocky plants 6 to 10 inches (15 to 25 cm) tall with no open flowers. A plant that is already flowering in its pot is under stress before it reaches the garden.

Tomato planting windows by region

The frost rule works across most of the country, but local calendars refine it where cool springs or hot summers change the picture.

Local planting windows where cool springs or summer heat shift the dates; a dash means no separate fall window is listed.

North and Upper Midwest (Zones 3 to 5). Plants go out in late May or early June, from seed sown around mid-April. Fargo and Denver have the latest windows in the city table, and both run into June.

Northeast. Wait at least a week or two after the last frost, until nights hold consistently above 45°F (7°C) as a bare minimum. In Massachusetts, the soil and daytime air should reach 60 to 65°F (16 to 18°C) first, and in New York City, nights in the 60s°F (16 to 21°C) are the signal. Tomatoes set out later catch up quickly, so waiting costs little.

Rocky Mountains and the Intermountain West. Late May is normal on the Colorado Front Range, once soil passes 55 to 60°F (13 to 16°C) and nights hold above 52°F (11°C).

Pacific Northwest. Frosts end early, but soil and nights stay cool into May. Plant May 1 to 10 in most of western Oregon and around mid-May in the Puget Sound area of western Washington. In central Oregon, wait until the second week of June and add 10 to 14 days to the maturity time on the seed packet.

California. The interior valleys plant from March to May overall, but around Sacramento transplants go out from mid-April into June. The south coast plants from April to mid-July.

Southeast. In Georgia, spring planting moves up to two to three weeks earlier in the south of the state and one to three weeks later in the north and mountains. Plant as early in the window as you safely can, because fruit set stops once summer nights stay warm.

Texas and the Gulf Coast. Around Houston, the ideal spring planting time runs from March 1 to mid-April, in step with the city table, and the fall crop goes in from late July to early August. Plant at the front of the spring window so most fruit sets before nights stay above about 75°F (24°C).

Frost-free areas and the low desert. In South Florida and California's Imperial and Coachella valleys, summer nights stay too warm for fruit set, so tomatoes are a fall-to-spring crop. South Florida plants from August through February and the desert valleys from December through March. Around Phoenix, plant in late winter, from mid-February to mid-March, and again from mid-July to August 1 for a fall crop.

Fall tomatoes in the South and low desert

Where the first fall frost comes late, a second crop planted in midsummer ripens in the cooler weeks of autumn. The deadline is set by maturity time: the variety needs its full days to maturity, counted from transplanting, plus time for the last fruit to ripen before the first fall frost. Fruit takes 25 to 35 days from flower to ripe, depending on temperature and variety.

The regional table gives the fall dates for each area. Georgia's July 20 deadline for the middle of the state shifts about two weeks later in south Georgia and two weeks earlier in the north.

Heat is the main obstacle for both the late spring crop and the young fall crop. Blossoms drop when nights stay above 70 to 75°F (21 to 24°C) or days pass 90 to 95°F (32 to 35°C), and no flowers set at 100°F (38°C). If it is already 90°F (32°C) by 10 a.m., the blossoms that open that day abort. Heat-set varieties such as 'Sun Leaper' and 'Solar Set' are bred to keep setting fruit through that heat, which helps both crops.

Varieties that change the timing

Days to maturity, counted from transplanting, decide whether a variety fits your season. Add about 25 days if you sow seed directly in the garden, which is rarely worth doing.

Days to maturity count from transplanting; a range means the figure varies from garden to garden.

In short-season gardens, early varieties are the difference between a harvest and a vine full of green fruit at the first frost. In the mountains, choose Early Girl or another variety that matures in 50 to 60 days. Around Puget Sound, pick varieties that mature in 75 days or less; Sun Gold and Stupice are proven there. 'Gold Nugget', 'Sweet Mojo', 'Cordova' and 'Roprechto Paste' are reliable early choices for western Oregon. In the cooler parts of New York, only early varieties may mature at all.

Long-season heirlooms such as Brandywine need a warm summer of 78 days or more after planting. Paste tomatoes such as San Marzano take about 80 days, so plant them at the start of your window. Cherokee Purple is a good compromise: an heirloom slicer that ripens in 72 days.

How to plant tomatoes outdoors

Planting itself goes quickly once the soil is warm and the plants are tough enough for full sun and wind.

1. Harden the plants off. Over one to two weeks, move seedlings to a sheltered outdoor spot for a couple of hours of sun a day, lengthening the time as they toughen. Bring them in on any night that threatens to approach freezing.
2. Warm the bed. Where springs are cool, cover the bed with black plastic before planting. It raises soil temperature by 5 to 6°F (about 3°C) and can bring the first harvest two to three weeks sooner. Clear plastic warms soil more, by 8 to 14°F (4 to 8°C).
3. Check the soil temperature. Plant only when the thermometer reads 60°F (16°C) at root-ball depth and the forecast shows nights above 50°F (10°C).
4. Plant on a cloudy, calm day or in the evening. Cooler, still air cuts water loss from the leaves while the roots settle, so plants wilt less.
5. Bury the stem. Set each plant so only the top two or three sets of leaves stay above ground. Lay leggy plants on their side in a trench 2 to 4 inches (5 to 10 cm) deep, or at a 30-degree slant with the top 5 to 6 inches (13 to 15 cm) showing. Roots grow along the buried stem, and a shallow trench keeps them out of soil below 6 to 7 inches (15 to 18 cm), which stays too cool for good root growth.
6. Space and support. Allow about 24 inches (60 cm) between plants. Compact determinate types can go 12 to 24 inches (30 to 60 cm) apart, staked indeterminates 14 to 20 inches (35 to 50 cm), and unstaked vines 24 to 36 inches (60 to 90 cm). Very vigorous indeterminates can need 4 feet (1.2 m). Put stakes or cages in now so you do not tear roots later. The plant spacing calculator works out how many fit in a bed.
7. Hold off on organic mulch. Leave straw or compost off until the soil passes 75°F (24°C), because a mulch layer keeps cool soil cool.

After planting, keep the soil evenly moist with 1 to 2 inches (2.5 to 5 cm) of water a week. Drought stress causes poor fruit set just as heat and cold do.

What happens if you plant too early or too late

Planting right at the median last frost is a common mistake, and it gains less than it seems. Half of years bring a later frost that can kill unprotected plants outright. Even without frost, cold soil and nights below 50°F (10°C) stall growth, and plants set out a couple of weeks later into warm soil often catch up.

Planting too late costs you in different ways depending on where you live. In the North, a long-season variety put in late may still be covered in green fruit when the first fall frost arrives. In the South and low desert, late spring plantings flower into summer heat and drop their blossoms. Fall crops planted after the deadline for your area may not ripen before frost.

Protecting tomatoes from a late frost or cold snap

When frost or a run of nights below 45 to 50°F (7 to 10°C) is forecast after planting, cover the plants before dark. Floating row cover, upturned buckets, plastic milk jugs and hot caps all hold in the day's warmth from the soil. Leave plants uncovered only once nights stay consistently above 45°F (7°C).

Walls of water, rings of water-filled plastic tubes, protect against a mild frost, which makes them useful for planting ahead of the window in the mountains and the Pacific Northwest. Plants under clear plastic row covers gain two to three times more heat than uncovered plants, which speeds growth in cool springs.

Once nights stay warm, the covers come off for good. From then on, green fruit keeps ripening on the vine as long as temperatures stay above 50°F (10°C) most of the time. Pick everything before the first fall frost, ripe or not. For the rest of the warm-season garden, see when to plant pumpkins and the full vegetable planting calendar, then map where each crop goes with Sow's garden planner.