Plant care
Tomatotemperature & humidity
Solanum lycopersicum
Ideal temperature for tomato
Tomato is happiest between 18-29°C (65-85°F). That is comfortably within normal household range, so the risk is rarely the average room temperature — it is the extremes: a leaf pressed against freezing winter glass, the hot dry updraft above a radiator, or the cold blast from an air-conditioning vent or a frequently-opened winter door. Below about 18°C growth stalls, and a cold snap a few degrees under that will cause chilling damage — soft, blackened, or translucent patches on the leaves within a day or two. Move tomato away from those micro-hazards before worrying about the thermostat.
Cold tolerance & winter care
Tomato is frost-tender (USDA Grown as an annual in zones 3-11, RHS H1c (tender; outdoors only in summer)). It cannot survive a frost, so in most of the US and UK it lives indoors year-round or summers outside and comes back in well before the first autumn frost — once nights drop toward 10-12°C is the cue, not the first frost warning. Acclimate it over a week when moving between indoors and out so the leaves do not shock.
Humidity for tomato
Tomato sits happiest at around 40-70% (outdoor) relative humidity. Outdoor humidity rarely matters; greenhouse growers ventilate to prevent disease. The usual low-humidity tell is crisp brown leaf tips and edges while the soil moisture is fine — a sign the air, not the watering, is the problem. If you need to raise it, the reliable methods are grouping plants together, standing the pot on a tray of damp pebbles (the pot above the waterline, never in it), or running a small humidifier in winter when indoor heating dries the air most. Misting is the least effective — it raises humidity for minutes, not hours.
Tomato temperature & humidity — frequently asked questions
What temperature is best for tomato?
Tomato grows best between 18-29°C (65-85°F). Keep it out of cold draughts, off freezing windowsills in winter, and away from the hot dry air directly above radiators — the extremes matter far more than the average room temperature.
How cold can tomato tolerate?
Tomato starts to suffer below roughly 18°C. It is frost-tender and will be damaged or killed by a frost, so bring it indoors once nights fall toward 10-12°C.
What humidity does tomato need?
Tomato prefers about 40-70% (outdoor) relative humidity. Outdoor humidity rarely matters; greenhouse growers ventilate to prevent disease.
How do I raise humidity for tomato?
Group it with other plants, stand the pot on a tray of damp pebbles (kept above the waterline), or run a small humidifier in winter. Misting only helps for a few minutes, so it is the weakest option for a plant that genuinely needs more humidity.
Can tomato live outside?
Tomato is rated for USDA zone Grown as an annual in zones 3-11 and RHS hardiness H1c (tender; outdoors only in summer). Outside that range it must come indoors before the first frost — treat any outdoor stint as a summer holiday, not a permanent home.
More tomato care
Temperature and humidity are one piece. See the full tomato care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.