Growing Tomatoes in Extreme Heat

Why heat makes the flowers drop

The failure isn't the plant wilting — it's pollination breaking down. Clemson explains that under high temperatures the pollen becomes tacky and nonviable, preventing proper pollination, so the flowers abort. Texas A&M adds that much of the poor fruit set in heat is simply a lack of pollination during high day and night temperatures.

The exact numbers differ by source and region, and it's worth citing them as they're stated rather than blending them. Clemson gives an optimum daytime range of 70 to 85°F, with several days of nights above 70°F or days above 85°F causing flower abortion, and blossom drop below 55°F or above 90°F for extended periods. Texas A&M's threshold is days above 90°F with nights above 75°F; Alabama's is days above 85°F with nights above 72°F, noting that for some varieties high night temperatures alone are enough to abort flowers. This is closely related to the general problem covered in tomato blossom drop and flowers falling off.

Time plantings around the heat

In a hot climate the goal is to have plants flowering when temperatures are in the setting range, not during the peak. Texas A&M advises setting spring transplants out as soon as frost danger passes so plants fruit before deep summer, and planting a fall crop about 120 days before the typical first frost so it blooms as temperatures fall again. In practice that means aiming for spring and fall harvest windows and treating the hottest weeks as a gap.

Heat-tolerant varieties matter more than technique here. Texas A&M defines a heat-tolerant variety as one that does best under high heat — 90°F or better — and can still set or continue to set fruit under hot conditions, and recommends picking varieties with some heat tolerance where midsummer temperatures are high. Choosing the right variety for your climate does more than any watering trick.

What actually helps in the moment

When the heat is already on, options are limited but real. Texas A&M suggests using heat-tolerant varieties if available or allowing some afternoon shade on the plants, while acknowledging there's very little you can do when extremely high temperatures persist for extended periods. Clemson's advice during a hot spell is simply to keep plants irrigated and wait for more favorable temperatures — the flowers that form once nights cool will set normally.

So don't panic over a flush of dropped blossoms in a heat wave; it's the weather, not a disease. Steady water, a bit of afternoon shade (see shade cloth for the vegetable garden), heat-set varieties, and patience carry the plant through to the next setting window. Sensible pruning can help airflow and manageability too — see how to prune tomato plants — and in tight or hot spots, best tomato varieties for containers points to compact, productive picks.

Sources

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

• Clemson Cooperative Extension HGIC — Why Did My Tomatoes Stop Producing Fruit? — The optimum daytime growing temperature range for tomatoes is between 70 and 85°F; several days of nighttime temperatures above 70°F and/or daytime temperatures above 85°F will cause the plants to abort flowers because the pollen becomes tacky and nonviable, preventing proper pollination; nighttime temperatures below 55°F will also prevent pollination; the recommendation during heat is to keep plants irrigated and wait for more favorable growing temperatures.
• Texas A&M AgriLife Extension — Growing Tomatoes Successfully on the Texas High Plains — Flowers may abort or blossoms drop when daytime temperatures are above 90°F and nighttime temperatures remain above 75°F, much of it due to lack of pollination; heat-tolerant varieties are those that do best under high heat (90°F or better) and are able to set or continue to set fruit under hot conditions; it is a good idea to use heat-tolerant varieties if available or allow some afternoon shade, as there is very little one can do when extremely high temperatures occur for extended periods; set spring transplants once frost danger passes and plant a fall crop about 120 days before the typical first frost.
• Alabama Cooperative Extension System — Blossom Drop in Tomato — When day temperatures exceed 85°F and night temperatures exceed 72°F tomato flowers often abort, and for some varieties night temperatures alone above 72°F can be detrimental to flowering; temperatures lower than 55°F can also inhibit fruit set.

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