Frost will kill tomato plants, but the timing depends on the type of frost and how cold it gets

Tomato plants die when exposed to frost because their cells contain water that freezes and ruptures the plant tissue. A light frost — temperatures between 29°F and 32°F — will damage leaves and soft stems but may not kill the whole plant if it lasts only a few hours. A hard freeze — temperatures of 28°F or below — kills tomato plants outright, usually within a single night. The plant cannot recover from a hard freeze; the damage is permanent.

Tomatoes are warm-season plants with no cold hardiness. Unlike perennials that go dormant in winter, tomatoes have no mechanism to survive freezing temperatures. Even a single night of frost can end your growing season if you do not protect the plants or harvest the fruit beforehand.

Key Takeaways

  • Light frost (29°F to 32°F) damages leaves and stems but may not kill the entire plant if it lasts only a few hours; hard freeze (28°F or below) kills tomato plants permanently.
  • Check your local frost date — the average date of the last spring frost and first fall frost in your area — to know when to plant and when to harvest.
  • You can protect tomato plants from light frost by covering them with blankets, sheets, or frost cloth before temperatures drop, but this does not work against a hard freeze.
  • Harvesting green tomatoes before a hard freeze and ripening them indoors is the most reliable way to save your crop when freezing weather is forecast.

How to find your local frost dates

Your frost date is the average date when frost occurs in your area. The "last spring frost date" is when you can safely plant tomatoes outdoors; the "first fall frost date" is when you should expect freezing temperatures to return. These dates vary by location — a city 50 miles away may have frost two or three weeks earlier or later than yours.

Find your frost dates by entering your zip code into the USDA Hardiness Zone map at planthardiness.ars.usda.gov or by searching "[your city] frost dates" online. Local garden centers and county extension offices also have this information. Once you know your dates, you can plan your planting and harvesting around them.

Protecting tomato plants from light frost

Light frost can be stopped with a physical barrier. Before temperatures drop, cover your tomato plants with blankets, old sheets, frost cloth, or even cardboard boxes — anything that traps heat and keeps frost from settling on the leaves. The cover must touch the ground on all sides to seal in warmth. Remove the cover during the day so the plant can photosynthesize and breathe.

Water the soil around the plants before covering them. Moist soil holds heat better than dry soil and releases that heat slowly through the night. Do not use plastic sheeting; it conducts cold and can damage plants if it touches the leaves.

This method works only for light frost lasting a few hours. If temperatures are forecast to drop to 28°F or below, or if frost is expected to last all night, covering will not save the plants. In that case, harvest what you can and prepare for the season to end.

Harvesting green tomatoes before a hard freeze

When a hard freeze is forecast, pick all the tomatoes on the plant — both ripe and green. Green tomatoes will ripen indoors over one to three weeks if stored correctly. This is the most reliable way to save your crop when freezing weather is coming.

Pick tomatoes that have started to show color (called the "breaker stage") first; these ripen fastest indoors. Then pick the fully green ones. Wash and dry them, then place them in a cardboard box or paper bag in a warm room — ideally 65°F to 75°F — away from direct sunlight. Check them every few days and remove any that show soft spots or mold. Ripe tomatoes can be moved to the refrigerator to slow further ripening.

Tomatoes ripened indoors will not taste quite as sweet as those ripened on the vine, but they are still edible and flavorful. This method also works if you want to harvest early for any reason — storm, pest pressure, or end of season.

Why tomatoes cannot survive freezing temperatures

Tomato plants evolved in warm climates and have no biological defenses against cold. When temperatures drop below freezing, the water inside the plant's cells turns to ice. Ice crystals puncture the cell walls, destroying the tissue. Once this happens, the plant cannot repair itself.

Some plants survive freezing by moving water out of their cells before ice forms, or by producing compounds that lower the freezing point of water inside the plant. Tomatoes do neither. Even if you bring a frozen tomato plant indoors and warm it up, the damage is done — the plant will not recover or produce new growth.

Planting tomatoes after the last spring frost

Do not plant tomatoes outdoors until after your last spring frost date has passed. Planting too early is one of the most common mistakes home gardeners make. Even if the weather seems warm for a few days, a late frost can kill young plants or stunt their growth so badly that they never recover.

If you start seeds indoors (which is common), harden them off — gradually expose them to outdoor conditions — for 7 to 10 days before planting them in the garden. This helps them adjust to wind, sun, and temperature swings. Keep seedlings indoors or under protection until your frost date has passed.

Extending the season in fall

To grow tomatoes as late as possible in fall, choose varieties that mature quickly — usually labeled as 50 to 70 days to maturity. Plant them in mid-summer so they produce fruit before the first fall frost arrives. You can also use row covers or cold frames to add a week or two to the season, but this only works against light frost.

Watch the weather forecast in late summer and early fall. When frost is predicted, harvest ripe and near-ripe tomatoes when ready. Green tomatoes can be ripened indoors, so there is no need to leave them on the plant hoping for one more warm spell.

Frequently Asked Questions

Can a tomato plant recover if it gets frosted once but survives?

Light frost may damage leaves and soft growth but not kill the whole plant. New leaves will grow back, but the plant will be set back by one to two weeks. If temperatures stay above freezing after that, the plant can continue producing. A hard freeze causes permanent damage — the plant will not recover.

What temperature kills tomato plants overnight?

A hard freeze at 28°F or below will kill tomato plants in a single night. Light frost at 29°F to 32°F damages foliage and may kill young plants, but mature plants sometimes survive if the frost lasts only a few hours and you cover them before it hits.

Should I pick tomatoes before they are fully ripe if frost is coming?

Yes. Pick any tomato showing color — even just a hint of orange or red — and any fully green tomatoes. Tomatoes at the breaker stage (first color showing) ripen indoors in one to two weeks. Fully green ones take longer but will ripen. This is better than losing the entire crop to frost.

Can I grow tomatoes in a greenhouse to avoid frost?

A greenhouse or cold frame extends the season and protects against light frost, but a hard freeze can still kill plants inside an unheated structure. If you use a greenhouse, monitor temperatures and use heaters or covers during hard freezes, or harvest the fruit before the freeze arrives.

Do different tomato varieties have different frost tolerance?

All tomato varieties are killed by hard freezes. Some varieties mature faster and can produce fruit before fall frost arrives, which is useful for short growing seasons. But no tomato variety is frost-hardy — they all need protection or harvest before freezing temperatures occur.