Best Temperature for Growing Tomatoes: Weather and Care Guide

Tomatoes are the most popular home-grown vegetable, and they are also fussy about weather. The same plant can give you baskets of fruit in mild weather and nothing but yellow flowers falling off in a heat wave.

Hardly any kitchen can do without tomatoes. They go into curry gravy, chutney, soup, salad, rasam and pasta sauce, and a ripe tomato from your own plant tastes sweeter and juicier than most store-bought ones, which are often picked early so they can travel.

This guide explains the temperatures tomatoes like, what goes wrong when it is too hot or too cold, and how to take care of them. If you are starting from scratch, first see how to grow tomatoes from seeds.

Tomatoes come from western South America, from the Andes in countries such as Peru and Ecuador. They were first grown as a crop in Mexico, where the Aztecs called them tomatl, and the Spanish took them to Europe in the 1500s. At first many Europeans were suspicious of them, but Italy and Spain fell in love with them, and today it is hard to imagine Italian food without tomato sauce. Tomatoes are believed to have reached India through Portuguese traders and are now used in almost every curry. China is by far the biggest producer of tomatoes, followed by India, and then countries like Turkey, the United States, Egypt and Italy.

The tomato is a warm-season crop that needs sun and moderate heat. In much of the Indian plains the main crop is grown in the cooler months, roughly October to February, and in the hills it is grown in summer, because extreme heat stops fruit from setting. In cooler countries like the UK, Canada and the northern US, tomatoes are planted after the last frost in spring and harvested from mid-summer until the first frost of autumn. In the Mediterranean, long, dry, sunny summers are ideal.

At a glance

Best temperature: 70-85°F (21-29°C) during the day and 55-70°F (13-21°C) at night
Seeds germinate best at 70-85°F (21-29°C), in 5-10 days
Ripening: best at 68-77°F (20-25°C)
Sunlight: 6-8 hours of direct sun
Pot: 5 gallon (19 L) or larger for one plant
Harvest: usually 60-85 days after transplanting, depending on variety

Benefits of tomatoes

Tomatoes are a good source of vitamin C, potassium and vitamin K, and they are rich in lycopene, the red pigment that works as an antioxidant. Interestingly, cooking tomatoes with a little oil makes lycopene easier for the body to absorb, which is one more reason a good tomato gravy is no bad thing. They are also mostly water, so they are hydrating and low in calories.

For a gardener, a tomato plant is very generous. One healthy plant can give several kilos of fruit over a season, and you can pick them at the stage you like: green for chutney and sabji, or fully red for salad.

Best temperature for tomatoes

Temperature is what makes or breaks a tomato crop. A lot of gardeners do everything right and still lose their flowers, simply because of a heat wave or a cold snap.

Day: 70-85°F (21-29°C).
Night: 55-70°F (13-21°C). Tomatoes like a small drop in temperature at night.
Soil: at least 60°F (16°C) before you plant out. Don’t rush into cold soil.
Transplant outdoors only after the last frost, when nights stay above about 50°F (10°C).

When it is too hot

Tomatoes struggle when days go above about 90°F (32°C), or when nights stay above about 75°F (24°C).

Flowers drop without making fruit, because pollen becomes sticky and less viable in heat.
Fruit ripens poorly. Above about 85°F (29°C) the red pigment doesn’t form well, and fruit turns yellow or orange instead of red.
Leaves may curl, and fruit may get sunscald.
What helps: afternoon shade with a 30% shade cloth, deep watering in the morning, a 2-3 inch (5-8 cm) mulch, and moving pots off hot concrete.

When it is too cold

Growth stops below about 50°F (10°C), and flowers drop when nights fall below about 55°F (13°C).
Frost kills tomato plants. Cover or bring pots inside when frost is forecast. See how to protect plants from frost.
At the end of the season, pick mature green tomatoes before the first frost and ripen them indoors.

Pot, soil and sunlight

Tomatoes need a big pot and a lot of sun, but they are not difficult once those two things are right.

Use a pot at least 5 gallon (19 L) for one plant, 12 inch (30 cm) or deeper, with drainage holes.
Fill with potting mix mixed with compost. See how to compost kitchen scraps.
Give 6-8 hours of direct sun. Less sun means fewer tomatoes.
Plant deep. Bury the stem up to the first set of leaves, because it grows extra roots.
Add a stake or cage when planting.

Watering and feeding

Water deeply 1-2 inches (2.5-5 cm) per week, more in hot weather. Keep watering even, because swings between dry and wet cause split fruit and blossom end rot.
Water the soil, not the leaves, in the morning.
Mulch to keep moisture steady.
Feed with compost at planting. Once flowers appear, use a tomato food that is lower in nitrogen and higher in phosphorus and potassium every 2-3 weeks.

Common problems

Flowers dropping: heat above 90°F (32°C), cold nights below 55°F (13°C), or too little water.
Black bottom on the fruit (blossom end rot): uneven watering. Water regularly and mulch.
Cracked fruit: heavy watering after dry periods.
Yellow lower leaves: normal as the plant ages. If widespread, check for overwatering or lack of feed.
Spots on leaves: early blight or fungus. Remove affected leaves, water at the base and improve air flow.
Large green caterpillars (hornworms) and aphids: pick them off by hand or spray with water or neem oil.

Frequently asked questions

What is the ideal temperature for tomato plants?

70-85°F (21-29°C) in the day and 55-70°F (13-21°C) at night.

Why are my tomato flowers falling off?

It is usually heat above 90°F (32°C), cold nights below 55°F (13°C), or uneven watering.

Can tomatoes grow in winter?

Only in warm climates or indoors under strong light. Outside, frost kills them, and below 50°F (10°C) growth stops.

Read the full guide to growing tomatoes from seeds, our kitchen garden guide for beginners and how to protect plants from frost.