Wyoming frost dates

Across Wyoming, the average last spring frost is around May 20 and the average first fall frost around September 15 — roughly 118 frost-free days. USDA zones 3a, 3b, 4a, 4b, 5a, 6a.

Risk you accept	Last spring frost by	First fall frost by
Cautious (~10%)	June 3	September 1
Average (~50%)	May 20	September 15
Gambler (~90%)	May 6	September 29

Wyoming spans a wide range of elevations and climates — your town’s dates can differ from the state average by two weeks or more. Look up your exact ZIP.

→ Turn these into sowing dates with the Wyoming planting calendar, or look up an exact ZIP code.

Statewide average from NOAA/NCEI freeze normals. Cautious/gambler dates are about two weeks either side of the average.