Plant tomatoes outdoors after your last spring frost date, when soil temperature reaches 60°F or higher
The single most important date for tomato planting is your last spring frost date—the average date of the final frost in your area. Tomatoes cannot survive frost. They stop growing below 50°F and die if exposed to freezing temperatures. You can find your frost date by searching "[your city] last frost date" or checking the USDA Plant Hardiness Zone Map for your zip code.
Beyond frost safety, soil temperature matters as much as air temperature. Tomato seeds and seedlings planted into cold soil will sit dormant, rot, or grow so slowly that pests and disease catch up to them. Wait until soil reaches at least 60°F before planting—ideally 65°F to 70°F for faster growth. You can measure soil temperature with a straightforward soil thermometer from any garden center, pushed 4 inches into the ground in the morning.
In most of the United States, this means planting between late April and late May. In warmer regions (southern California, southern Texas, southern Florida), you may plant in March or even February. In cooler regions (northern New England, the upper Midwest, Montana), you may not plant until June. The timing varies by location, not by calendar month.
Key Takeaways
- Your last spring frost date is the hard important date—tomatoes planted before that date will likely die if frost returns.
- Soil temperature must reach 60°F or higher; cold soil causes seedlings to rot or stall, even if air temperature feels warm.
- Check your specific frost date online using your zip code, because planting dates vary by 4 to 8 weeks across the country.
- Hardening off seedlings (gradually exposing them to outdoor conditions) for 7 to 10 days before planting reduces transplant shock.
- If you plant too early and frost threatens, cover plants with blankets or row covers the night before the freeze.
How to find your last frost date
The USDA Plant Hardiness Zone Map divides the United States into zones based on average annual minimum winter temperatures. Each zone has a corresponding last frost date. Enter your zip code at planthardiness.ars.usda.gov, and the map will show your zone and the frost date range for your area.
If you prefer a faster search, type "[your city name] last frost date" into a search engine. Local nurseries and county extension offices also publish this date for their areas. Once you have the date, mark it on a calendar—that is your earliest safe planting day for tomatoes outdoors.
Soil temperature and why it matters more than air temperature
A warm day in April can fool you. The air temperature might hit 70°F, but if the soil is still 45°F, tomato roots will not absorb water or nutrients. The plant sits in the ground, weakened, while fungi and bacteria attack the stem. This is why tomatoes planted too early often rot at the soil line or straightforward fail to grow.
Buy a soil thermometer (they cost $8 to $15) and check the temperature 4 inches deep in the morning, before the sun warms the surface. Wait until the reading is 60°F or higher. In most regions, soil reaches this temperature 1 to 3 weeks after the last frost date, so you are not usually waiting long.
Planting seedlings versus seeds outdoors
Most home gardeners buy seedlings (small plants already 6 to 8 weeks old) from a nursery rather than starting seeds indoors. Seedlings are planted outdoors on or just after the last frost date, once soil is warm enough. If you start seeds indoors under lights, sow them 6 to 8 weeks before your frost date so they are ready to transplant when soil warms.
Seedlings need hardening off—a 7 to 10 day period where you gradually expose them to outdoor sun, wind, and temperature swings. Start by placing them outside in shade for 2 to 3 hours, then increase sun exposure and time outdoors each day. This toughens the plant and prevents wilting or sunburn when you plant it in the garden.
What to do if frost threatens after you plant
Sometimes frost returns after you have planted. If a frost warning is issued for your area, cover plants with blankets, burlap, or commercial row covers the evening before the freeze. Drape the cover loosely so it does not touch the leaves, and remove it the next morning once temperatures rise above 32°F. This straightforward step can save a crop.
Water plants thoroughly before covering them—moist soil holds heat better than dry soil. If you do not have covers on hand, even old bedsheets work in a pinch. The goal is to trap the warmth radiating from the soil and slow heat loss from the plant.
Regional planting timelines
Planting dates shift significantly across the country. The table below shows approximate windows for major regions, but your specific frost date is more reliable than any general range.
| Region | Approximate Last Frost Date | Typical Planting Window |
|---|---|---|
| Southern Florida, Southern Texas, Southern California | February to March | February to April |
| Mid-Atlantic (Virginia, North Carolina, Maryland) | April 15 to May 1 | Late April to mid-May |
| Upper Midwest (Minnesota, Wisconsin, Michigan) | May 15 to June 1 | Late May to early June |
| Northern New England (Maine, Vermont, New Hampshire) | May 20 to June 10 | Early June to mid-June |
| Mountain West (Colorado, Montana, Wyoming) | May 15 to June 15 | Late May to mid-June |
Frequently Asked Questions
Can I plant tomatoes in March or April if it feels warm outside?
Not safely. Even if daytime temperatures reach 70°F or 80°F, frost can return at night, killing your plants. Check your last frost date first. If frost is still possible in your area, wait. Planting too early and losing seedlings to frost costs more time and money than waiting two or three weeks.
What if I do not know my exact frost date?
Search your zip code on the USDA Plant Hardiness Zone Map at planthardiness.ars.usda.gov, or call your local county extension office. They can tell you the frost date for your specific area in minutes. This is worth the effort because the date varies by location, sometimes by weeks.
Can I plant tomatoes in a greenhouse or indoors earlier than outdoors?
Yes. Greenhouses and indoor grow lights let you start seeds 6 to 8 weeks before your outdoor frost date. The seedlings stay warm and protected until soil outdoors is warm enough to transplant them. This gives you a head start on the growing season without risking frost damage.
What happens if I plant tomatoes in cold soil?
Cold soil slows root growth and water uptake. Seedlings may rot at the soil line, turn purple or yellow, or straightforward sit dormant for weeks. Even if they survive, they are weak and vulnerable to pests and disease. Waiting for warm soil produces healthier, faster-growing plants.
Is there a latest month to plant tomatoes?
Yes. Tomatoes need 60 to 85 days to produce ripe fruit, depending on the variety. Plant late enough that the plant has time to mature before the first fall frost. In most regions, this means planting by mid-June at the latest, though warmer areas can plant into July.