When is the last frost in Alma, CO?

For ZIP code 80420, the average last spring frost (32°F) is June 16, based on NOAA 1991-2020 climate normals for the Fairplay S Park Rd, CO weather station. There is a 1-in-10 chance of a frost after June 30.

When is the first frost in Alma, CO?

The average first fall frost (32°F) is September 9. There is a 1-in-10 chance of frost by August 21, so tender plants are at risk from that point on.

How long is the growing season in 80420?

In half of years, the frost-free season (between the last and first 32°F frost) is at least 83 days long.

Are these frost dates a forecast?

No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.

Frost dates for 80420Alma, CO

The average last spring frost in Alma is June 16 and the average first fall frost is September 9, giving a typical growing season of about 83 days. Dates are based on NOAA 1991-2020 climate normals.

Average last spring frost: Jun 16
Average first fall frost: Sep 9
Growing season: 83 days

Frost risk by date

NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.

Spring dates: chance of a frost AFTER the date. Fall dates: chance of a frost BEFORE the date.
Temperature	Last spring: 90% / 50% / 10% chance	First fall: 10% / 50% / 90% chance	Growing season (50%)	Years with at least one
Light frost (36°F)	—	—	47 days	100%
Frost / freeze (32°F)	Jun 2 · Jun 16 · Jun 30	Aug 21 · Sep 9 · Sep 24	83 days	100%
Hard freeze (28°F)	May 21 · Jun 2 · Jun 17	Sep 6 · Sep 21 · Oct 3	107 days	100%

Where these dates come from

ZIP code 80420 is matched to the NOAA station Fairplay S Park Rd, CO, 9.1 km away, at 9,996 ft elevation (363 ft lower than the ZIP code's center). Nearby stations for comparison:

Station	Elevation	Avg last frost	Avg first frost
Fairplay S Park Rd, CO (used)	9,996 ft	Jun 16	Sep 9
Climax, CO	11,345 ft	—	—
Leadville Lake Co Ap, CO	9,933 ft	—	—
Sugarloaf Rsvr, CO	9,738 ft	—	—

Frost dates near Alma

Fairplay, CO 80440 · last Jun 16, first Sep 9
Leadville, CO 80461 · last —, first —
Breckenridge, CO 80424 · last Jun 6, first Sep 19
Climax, CO 80429 · last —, first —
Como, CO 80432 · last —, first —
Frisco, CO 80443 · last —, first —
Jefferson, CO 80456 · last Jun 15, first Sep 9
Granite, CO 81228 · last Jun 16, first Sep 10

Frequently asked questions

When is the last frost in Alma, CO?: For ZIP code 80420, the average last spring frost (32°F) is June 16, based on NOAA 1991-2020 climate normals for the Fairplay S Park Rd, CO weather station. There is a 1-in-10 chance of a frost after June 30.
When is the first frost in Alma, CO?: The average first fall frost (32°F) is September 9. There is a 1-in-10 chance of frost by August 21, so tender plants are at risk from that point on.
How long is the growing season in 80420?: In half of years, the frost-free season (between the last and first 32°F frost) is at least 83 days long.
Are these frost dates a forecast?: No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.