Plant tomatoes after your last spring frost date, when soil temperature reaches 60°F

The single most important rule for tomato planting is this: soil must be warm. Tomato seeds and seedlings will rot in cold, wet soil, and they grow so slowly in cool conditions that you lose weeks of growing time. Your last spring frost date is the average date of the final frost in your area—after that date, the soil begins to warm reliably. You can find your frost date by entering your zip code at the National Weather Service website or asking at a local garden center or cooperative extension office.

Soil temperature matters more than air temperature. A thermometer stuck 2 inches into the soil should read at least 60°F before you plant seeds directly in the ground. If you are transplanting seedlings you started indoors, wait until soil reaches 65°F to 70°F for best results. Even if the air feels warm on a spring day, the soil underneath may still be cold from winter. Planting too early is the most common reason tomato seedlings fail.

Key Takeaways

  • Plant tomatoes after your last spring frost date when soil temperature is at least 60°F for seeds or 65°F to 70°F for seedlings.
  • Check your local frost date through the National Weather Service website or your county cooperative extension office.
  • Start seeds indoors 6 to 8 weeks before your frost date if you want to transplant seedlings rather than direct-seed.
  • Soil temperature is more reliable than air temperature—use a soil thermometer to check before planting.
  • In warm climates with no spring frost, you can plant tomatoes in late winter or early spring when soil warms above 60°F.

How to find your last spring frost date

Your last spring frost date depends on where you live. The continental United States ranges from late April in the coldest zones (northern Minnesota, Maine, Montana) to mid-February in the warmest zones (southern Florida, southern Texas, southern California). The National Weather Service publishes frost date maps by county, and you can search your location at weather.gov.

If you do not have internet access, call your county cooperative extension office—the number is listed under county government in your phone book or online. They can tell you the frost date and often have other local planting information specific to your soil and climate. Local garden centers also know the frost date for your area and can answer questions about varieties that grow well nearby.

Starting seeds indoors versus direct seeding

You have two paths: start seeds indoors under lights 6 to 8 weeks before your frost date, or plant seeds directly in the garden after the frost date when soil is warm. Most home gardeners start seeds indoors because it gives them a head start on the growing season and lets them choose from more varieties than garden centers stock as seedlings.

If you start seeds indoors, you will transplant seedlings into the garden around your frost date, once they have developed their first true leaves (the second set of leaves that appear). Seedlings started indoors are more forgiving of slightly cool soil than seeds are, but they still perform better when soil reaches 65°F to 70°F. If you direct-seed in the garden, wait until soil is at least 60°F and ideally closer to 70°F, because seeds need warmth to germinate.

Checking soil temperature with a thermometer

A soil thermometer costs $5 to $15 at any garden center or online. Push it 2 inches into the soil in the spot where you plan to plant, wait 2 to 3 minutes, and read the temperature. Do this in the morning after the sun has warmed the soil for a few hours but before the hottest part of the day. Check the same spot on several days to see if temperature is rising steadily.

Soil warms faster in raised beds and in soil that has been loosened and amended with compost. Dark soil absorbs more heat than light soil. If your soil is still cold but your frost date has passed, you can warm it faster by laying black plastic or landscape fabric over the bed for a week or two before planting. Remove the plastic before you plant, or cut holes in it for the seedlings.

Regional timing examples

In the upper Midwest (Minnesota, Wisconsin, Michigan), the last frost date falls around May 15 to May 30. Soil usually reaches 60°F by late May or early June. If you start seeds indoors in mid-March, you will transplant seedlings in mid-May, and they will be ready to go in the ground by early June when soil has warmed.

In the mid-Atlantic (Pennsylvania, Maryland, Virginia), the last frost date is around April 20 to May 10. Soil reaches 60°F by mid-May. Start seeds indoors in late February or early March to transplant by mid-April, with planting in the garden by late April or early May.

In the South (Georgia, South Carolina, North Carolina), the last frost date is around April 1 to April 15. Soil warms by mid-April. You can start seeds indoors in January or early February and plant seedlings outside by mid-April.

In warm climates with no spring frost (southern Florida, southern Texas, southern California), you can plant tomatoes whenever soil temperature is above 60°F. This may be as early as late January or February. Some gardeners in these areas plant a spring crop and a fall crop, timing the fall planting so tomatoes mature before the first cold snap in late fall or early winter.

What happens if you plant too early

Planting tomato seeds or seedlings in cold soil causes several problems. Seeds may rot before they sprout. Seedlings turn purple or dark red, stop growing, and may die. Even if they survive, they grow so slowly that you do not gain any time—a seedling planted 3 weeks early in cold soil will often be smaller than one planted at the right time in warm soil. Cold soil also invites fungal diseases like damping-off, which kills seedlings at the soil line.

If you have already planted and the soil is too cold, the safest move is to pull the seedlings and replant them in 2 to 3 weeks when soil has warmed. It feels wasteful, but it works better than watching them struggle for weeks.

Hardening off seedlings before planting

If you started seeds indoors under lights, seedlings need to adjust to outdoor conditions before they go in the ground. This process is called hardening off. Begin 7 to 10 days before planting by setting seedlings outside in a sheltered spot for 1 to 2 hours on a mild day. Each day, leave them out a little longer and expose them to more direct sun and wind. By planting day, they should spend a full day outside.

Hardening off prevents transplant shock and sunburn (pale patches on leaves that turn brown). Seedlings that skip this step often wilt badly when planted and take weeks to recover, even if soil temperature is perfect.

Frequently Asked Questions

Can I plant tomatoes if the air is warm but soil is still cold?

No. Warm air does not warm soil fast enough. Tomato seeds and seedlings will rot or grow so slowly that you lose the advantage of planting early. Wait until soil reaches 60°F, even if the air temperature is 75°F or higher. A soil thermometer takes the guesswork out.

What if I cannot find my exact frost date?

Call your county cooperative extension office or ask a local garden center. If neither is available, use the National Weather Service website (weather.gov) and search your county. You can also ask neighbors who garden—they know from experience when it is safe to plant in your area.

Can I plant tomatoes in a container earlier than in the ground?

Containers warm faster than ground soil, so you can plant a few weeks earlier if you use a large pot (at least 5 gallons) and place it in full sun. However, the soil still needs to reach 60°F. Use a soil thermometer to check the container soil, not the air temperature.

What if my area has an unusually cold spring?

Soil temperature is what matters, not the calendar date. If spring is cold and wet, soil may not reach 60°F until 2 to 3 weeks after your average frost date. Check soil temperature before planting rather than planting by the calendar. A late planting in warm soil beats an early planting in cold soil.

Do I need to wait for the frost date if I am growing tomatoes indoors?

No. Indoor tomatoes under grow lights are not affected by frost or outdoor soil temperature. You can start seeds indoors anytime and grow them year-round under lights. The frost date matters only if you plan to move seedlings outside.