Seed germination temperature chart

Soil temperatures in degrees Fahrenheit for 13 common vegetables, as published by Alabama Cooperative Extension.

Vegetable	Minimum	Best range	Maximum	Best single temperature
Tomato	50	70 to 95	95	85
Pepper	60	65 to 95	95	85
Lettuce	35	40 to 80	85	75
Cabbage	40	45 to 95	100	85
Cucumber	60	60 to 95	105	95
Squash	60	70 to 95	100	95
Onion	35	50 to 95	95	75
Eggplant	60	75 to 90	95	85
Carrot	40	45 to 85	95	80
Spinach	35	45 to 75	85	70
Snap bean	60	65 to 85	95	80
Lima bean	60	60 to 85	85	85
English pea	40	40 to 75	85	75

Broccoli and basil are not in the source table. Check the seed packet for those.

How to use it

Warm-season crops such as pepper, eggplant, squash and tomato have high minimums. In a cool room they germinate slowly or not at all, which is when a heat mat helps. See the heat mat guide.
Cool-season crops such as lettuce, spinach and peas germinate from the 30s and 40s, and the table shows maximums in the 80s. A warm shelf can work against them.
Oklahoma State says to move seedlings off the heat mat once they germinate and put them under plant lights.
Measure the soil, not the room. Evaporation lowers soil temperature, and the University of Arizona says it can drop it by 5 to 10 degrees.

Sources checked 2026-10-14. Pages on this site are researched, not hands-on tested.