Tomatoes Staying Green: Why Heat Stalls Ripening

The heat pauses pigment production

Ripening color comes from pigments the plant builds as the fruit matures, and that chemistry has a comfortable temperature window. Purdue Extension puts the optimum ripening range at 68 to 77 degrees F and notes that above 85 degrees F the plant does not produce lycopene and carotene at all. That is why a run of days in the 90s can leave you with big, healthy, stubbornly green or pale-orange tomatoes.

Because it is the temperature, not the plant, that is stalled, there is nothing to spray or fertilize. Depending on the variety, heat-stalled fruit may ripen unevenly or turn more yellow-orange than deep red once it finally colors up. When cooler weather returns, the fruit generally resumes ripening on its own.

What you can do while you wait

• If a mature green or blushing tomato is stuck in a heat wave, pick it and ripen it indoors; Purdue suggests holding fruit around 60 to 65 degrees F, a bit warmer for faster ripening.
• Keep soil evenly moist so heat stress does not add a second problem on top of the stall.
• Leave some leaf canopy over the fruit rather than stripping the plant, so ripening tomatoes are not baking in direct sun.
• Give it time once temperatures drop back toward the 70s; on-vine ripening usually restarts without any intervention.

Sources

Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.

• Purdue Extension - Tomatoes Not Ripening? — The optimum temperature range for ripening mature green tomatoes is 68 to 77 F; tomatoes do not produce lycopene and carotene when temperatures are above 85 F; store mature green to slightly blushed fruit at 60 to 65 F to ripen indoors.
• SDSU Extension - Will Heat Make My Tomatoes Ripen Faster? — Excessive heat slows or stops tomato ripening because the pigments that turn fruit red are not produced at high temperatures; moderate temperatures ripen fruit best.
• Illinois Extension - Stalled Green Tomatoes: Why Won't They Turn Red? — High temperatures interfere with production of the pigments that ripen tomatoes, so fruit can stall at the mature green stage during hot weather and resume ripening when it cools; picking and ripening indoors is an option.

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