Yes, you can plant tomatoes in August, but success depends on your location and growing season

Planting tomatoes in August is possible in most of the United States, but the outcome hinges on how many frost-free days remain before winter. Tomatoes need 60 to 85 days from transplant to first ripe fruit, depending on the variety. If your first frost arrives in late October, August planting gives you a narrow window. If frost comes in September, you will harvest green tomatoes or none at all. The farther south you live, the more viable August planting becomes.

The real constraint is not the calendar—it is the plant's need for warm soil and air. Tomatoes stop growing when temperatures drop below 50°F at night. They produce no fruit when nighttime temperatures fall below 55°F. An August planting in the upper Midwest or Northeast will almost certainly fail to mature fruit before cold arrives. In the Deep South, Gulf Coast, or warm parts of the Southwest, August planting can work because frost does not arrive until November or December.

Key Takeaways

  • August planting works only if you have at least 70 frost-free days remaining before your first expected frost date.
  • Transplants (seedlings) mature faster than seeds, so starting with young plants rather than seeds gives you the best chance in August.
  • Choose fast-maturing varieties labeled 60 to 70 days to maturity, not the 80 to 90-day heirloom types.
  • Soil temperature matters more than air temperature—wait until soil is at least 60°F, ideally 65°F or warmer, before planting.
  • August-planted tomatoes often produce fewer total fruits than spring plantings because they have less time to grow before cold stress slows production.

Check your frost date before you plant

Your first frost date is the single most important number for August planting. This is the average date of the first killing frost in your area—the night when temperatures drop to 32°F or below. You can find your frost date through your county's cooperative extension office, or by searching online for "[your city] first frost date." Write down the date and count backward to today. If fewer than 70 days remain, August planting is a gamble.

Frost dates vary by elevation, proximity to water, and local geography. A city's official frost date is an average, not a may provide. Some years frost arrives two weeks early; other years it holds off. If your frost date is November 1 and today is August 15, you have roughly 78 days—enough for a fast variety. If your frost date is October 15, you have only 61 days, which is tight and risky.

Use transplants, not seeds, for August planting

Starting tomatoes from seed in August almost never works in time. Seeds need 6 to 8 weeks indoors before they are large enough to transplant outside. By the time a seed-grown seedling is ready, frost may already be near. Buy transplants (also called seedlings or starts) from a garden center instead. These are young plants already 4 to 8 inches tall, ready to go in the ground when ready.

Transplants cut 6 to 8 weeks off the timeline, which is the difference between harvesting fruit and harvesting nothing. A transplant planted in mid-August in a warm climate can flower by late September and produce ripe fruit by late October or early November. The same variety grown from seed would still be a small plant when frost arrives.

Choose fast-maturing varieties

Not all tomato varieties mature at the same speed. Heirloom and beefsteak types often need 80 to 90 days or more. Cherry tomatoes and determinate (bush) varieties often mature in 60 to 70 days. For August planting, choose varieties labeled 60 to 75 days to maturity. Check the seed packet or plant label for the days-to-maturity number.

Fast varieties include 'Early Girl' (52 to 62 days), 'Stupice' (60 to 70 days), 'Sungold' (57 to 70 days), and 'Glacier' (55 to 65 days). These are real options at most garden centers. Avoid 'Brandywine', 'Cherokee Purple', 'Mortgage Lifter', and other heirlooms, which need 75 to 90 days and will not mature in time for an August start in most climates.

Plant in warm soil and full sun

Tomato roots do not grow in cold soil. Soil temperature matters more than air temperature in August. Wait until soil temperature reaches at least 60°F, ideally 65°F or warmer. You can measure soil temperature with a soil thermometer, which costs $10 to $20 at any garden center. Stick it 4 inches into the ground in the morning and read it after 10 minutes.

Plant in full sun—at least 6 to 8 hours of direct sunlight daily. In August, the sun is lower and days are shorter than in spring, so every hour of light counts. Afternoon shade in very hot climates (over 95°F regularly) can prevent heat stress, but in most places, full sun is essential for fruit production before cold arrives.

Water and fertilize consistently through fall

August-planted tomatoes need steady water as they establish roots and grow. Water deeply 2 to 3 times per week, depending on heat and rainfall. Inconsistent watering causes blossom-end rot and cracking. Mulch around the base with 2 to 3 inches of compost or straw to retain moisture and keep soil temperature stable as air temperatures cool.

Fertilize every 2 to 3 weeks with a balanced fertilizer or one higher in phosphorus and potassium (the second and third numbers on the package). Nitrogen-heavy fertilizers promote leaves at the expense of flowers and fruit. Stop fertilizing 4 to 6 weeks before your expected first frost, so the plant focuses energy on ripening existing fruit rather than growing new leaves.

Harvest green tomatoes before frost and ripen them indoors

If frost is forecast before your tomatoes fully ripen, pick them when they show color—even if they are still mostly green or orange. Tomatoes ripen off the vine as long as they have started to change color. Place them in a cardboard box or paper bag at room temperature (65°F to 75°F is ideal) in a dark or dimly lit spot. They will continue to ripen over 1 to 3 weeks.

Fully green tomatoes picked before any color change will not ripen indoors and will taste bland. But tomatoes that have begun to blush pink, orange, or yellow will mature to full color and flavor indoors. This is a common and reliable way to salvage an August planting when frost arrives earlier than hoped.

Frequently Asked Questions

Can I plant tomatoes in August in the Northeast?

It is risky. Most of the Northeast has a first frost date between September 15 and October 15. That leaves only 30 to 60 days, which is not enough for most varieties to produce ripe fruit. If you want to try, choose the fastest varieties (50 to 60 days) and use transplants, not seeds. Expect to harvest mostly green tomatoes and ripen them indoors.

What if I plant in a container instead of the ground?

Container soil warms and cools faster than ground soil, which can be an advantage in August. Use a pot at least 5 gallons for a determinate variety, 10 gallons for an indeterminate type. Container tomatoes dry out faster, so you will need to water more often—sometimes daily in hot weather. The faster soil temperature changes also means container plants are more vulnerable to early cold snaps.

Do August-planted tomatoes produce as much fruit as spring-planted ones?

No. August-planted tomatoes have less time to grow before cold stress slows flowering and fruit production. They typically produce 30 to 50 percent fewer fruits than spring plantings. If you are looking for a large harvest, spring planting is more reliable. August planting is better for filling a gap or extending the season in warm climates.

Should I use a grow light or heat mat for August transplants?

No. August has plenty of natural light and warm soil. Grow lights and heat mats are for indoor seed starting in winter and early spring. In August, transplants need full outdoor sun and warm ground. A heat mat would actually overheat the soil and stress the plant.

What happens if I plant tomatoes too late in August?

If you plant after mid-August in most climates, the plant will not have time to flower and set fruit before cold arrives. You will get a large green plant with few or no tomatoes. The later you plant, the more likely you are to harvest only foliage and green fruit. Check your frost date and count backward at least 75 days before planting.