Frost dates in Wyoming

Across Wyoming's 129 NOAA stations with a frost every year, the typical last spring frost ranges from April 28 at Basin (3,840 feet above sea level) to June 24 at Moose 1 NNE (6,470 feet above sea level). The middle station's date is May 20.

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Last frost across Wyoming

The frost-free season runs from 63 days at Moose 1 NNE to 164 days at Basin.

The station with the latest frost sits about 2,600 feet higher than the one with the earliest.

At 29 stations, all high or far north, frost is possible in every month.

These are typical dates: in half of springs the last frost comes later. Each place's page, and each ZIP code lookup, also gives the late-year date, after which only 1 spring in 10 has a frost. That's the safer date for tender plants.

Frost dates for Wyoming's larger places

Typical (1-in-2) dates. Each place's page has the early and late years, a planting calendar and a printable planner. Zones are for the ZIP code nearest each place's center.

Hardiness zones in Wyoming

Wyoming's 189 ZIP codes in the USDA list fall in zones 4a to 5b: 4a (5 percent), 4b (23 percent), 5a (57 percent) and 5b (15 percent). Compared with the 2012 map, 53 percent of them moved to a warmer half zone (15 by a full zone or more), 42 percent stayed the same and 8 moved to a colder one.

A hardiness zone is about the coldest night of winter, which decides which shrubs, trees and perennials survive. Frost dates are about spring and fall, which decide when to plant. You need both. Read more about what the zones mean and what changed in 2023.

Every NOAA station in Wyoming

All 158 stations in Wyoming with frost statistics in NOAA's 1991 to 2020 normals, from A to Z. Station names are usually a town, an airport, or a distance and direction from a town. Find one near you and at a similar elevation.

Typical (1-in-2) dates at 32°F. For the early and late years, and a planting calendar built from your own dates, look up your ZIP code.