killing frost
A hard frost cold enough to wipe out tender crops.
Also called hard frost, killing freeze.
Updated September 24, 2026
killing frost pronunciation
/KILL-in FRAWST/
Meaning
Not a light white dusting on the grass. A killing frost is the cold snap that blackens tomato vines, knocks the garden out, and ends the growing season. Farmers and backyard growers watch the forecast for it each fall and spring. Agronomists often tie a true plant-killing freeze to around 28 degrees, colder than a mild frost that only nips leaves.
How folks use it
- “We covered the tomatoes last night before that killing frost hit.”
- “First killing frost usually finishes the garden around here.”
Origin and etymology
Straight farm English: frost that kills. Used across rural America, including Southern and Appalachian gardens and fields. Extension services still separate a light frost from a killing frost when they talk crop damage.
Frequently asked questions
Is every frost a killing frost?
No. A light frost may burn leaves. A killing frost takes the plant down for good.