Why Are My Tomatoes Not Ripening?
Tomatoes commonly stop ripening when daytime temperatures stay above 90°F or nights stay above about 70°F, because the pigments that make fruit red form poorly in prolonged heat. Fruit also ripens slowly in cool weather, heavy shade, or late in the season, but mature green tomatoes can finish ripening indoors.
First confirm that the fruit is mature green rather than still enlarging. A mature tomato is full-sized, glossy, and usually changes from deep green to a paler green, sometimes with a whitish or yellowish cast at the blossom end. Once that color break begins, it can ripen off the vine without a major loss of quality.
Heat is a frequent summer cause in much of the United States. Tomatoes set fruit well in warm weather, but sustained temperatures above 90°F can delay red pigment development, especially when warm nights continue. Keep plants evenly watered and mulched, and wait for a cooler stretch rather than stripping healthy leaves that shade the fruit.
Too much nitrogen can produce dense, vigorous foliage while delaying maturity. Avoid repeatedly feeding established tomato plants with high-nitrogen lawn or general garden fertilizers. After fruit has set, use soil-test guidance and focus on steady moisture rather than trying to force ripening with extra fertilizer.
Sunlight matters, but exposed fruit can sunscald in intense summer conditions. Tomato plants generally need at least six to eight hours of direct sun, with enough healthy foliage to cover fruit. Prune only diseased leaves and small amounts of crowded growth; severe pruning can expose fruit and reduce the plant's ability to finish the crop.
As autumn approaches, watch the local first-frost date. About four to six weeks before that date, remove new flowers and very small fruit that cannot reasonably mature, so the plant directs energy to existing full-sized tomatoes. Protect plants from a light frost with row cover, but remove it during the day when temperatures rise.
To ripen mature green fruit indoors, harvest it with the stem scar intact and place it in a single layer at roughly 60°F to 70°F. Keep it out of direct sun and check daily, removing any fruit that softens or shows decay. Do not refrigerate unripe tomatoes, because cold temperatures can reduce flavor and prevent normal ripening.
Frequently asked questions
Will putting green tomatoes on a sunny windowsill ripen them faster?
No. Warm room temperatures, not direct sunlight, drive ripening. A shaded counter at about 60°F to 70°F is more dependable.
Should I pick tomatoes before a heat wave?
Pick fruit that is full-sized and beginning to lighten in color. Leave clearly immature green fruit on the plant if conditions and season length allow.
Why are my tomatoes yellow instead of red?
Some cultivars ripen yellow, orange, pink, or striped. If a normally red tomato stays pale during hot weather, high temperatures may be delaying its red color.
General guidance for US home gardens. Conditions vary by region and season; check with your local Cooperative Extension office for site-specific advice. Page updated Aug 4, 2026.