Colorado Last Frost Dates: 10%, 50% and 90% Odds by Station

2026-10-14

Colorado has one of the widest frost-date spreads in the country. Among the 210 Colorado stations in NOAA’s 1991-2020 normals, the median last spring freeze (32°F) ranges from April 14 at the warmest station to June 21 at the coldest. The median first fall freeze runs from September 2 to October 26. Elevation drives most of that, so the “Colorado frost date” you see quoted elsewhere tells you very little.

For your exact address, enter your ZIP code in the frost date lookup. The tables below show what the data looks like across the state. For other states, see last frost dates by state.

TL;DR:

• Across 210 Colorado stations, the median last spring freeze (32°F) runs from April 14 to June 21, and the median first fall freeze from September 2 to October 26.
• Downtown Denver’s station has a median last 32°F night of April 30, with a 10% chance of a freeze after May 13.
• Most Front Range cities have a median last freeze in early May. Waiting until mid-May cuts the odds of a later freeze to about one in ten.
• Grand Junction runs about two weeks earlier than the Front Range, and Durango about three weeks later.

Frost dates for Colorado’s major cities

Six city stations

These are the stations our ZIP lookup matches to a downtown ZIP code in each city:

Along the Front Range, most cities have a median last freeze in early May, and waiting until mid-May cuts the odds of a later freeze to about one in ten. Grand Junction, lower and in the western valleys, runs about two weeks earlier. Durango is about three weeks later.

How to read the tables

• Last 32°F (spring): 90% / 50% / 10%. This is the chance of at least one more freeze after each date. The 50% date is the usual “last frost date,” a coin flip.
• First 32°F (fall): 10% / 50% / 90%. This is the chance the first fall freeze has already come by each date.
• Median season: NOAA’s median number of days between the last spring and first fall 32°F night.
• Data: NOAA’s completeness flag. Where the spring and fall flags differ, we show the weaker one. In Colorado they never differ.
  • S (standard): 24+ years of data.
  • R (representative): 10+ years.
  • In both cases, NOAA fills gaps from surrounding stations.
  • E (estimated): at least 2 years of data, with the normals estimated statistically from nearby standard stations. Treat E stations with more caution. None appear in the statewide table below, but 12 are in the full list.

Need odds for a date that isn’t listed? See frost odds after any date.

Colorado frost dates across the state

One station per area

One station per 1° × 1° area of the state (about 30 areas), chosen for the most complete data. Sorted alphabetically.

What stands out

• Elevation matters more than latitude. Holyoke, in the far northeast at 1,152 m, has a median last freeze of May 11. Alamosa, much farther south but at 2,296 m in the San Luis Valley, has June 7.
• High valleys have very short seasons. Cochetopa Creek (2,440 m) has a median of 74 days between the last and first 32°F nights. Kremmling, Bailey and Maybell are all under 85 days. In places like these, even early-summer plantings of tender crops need frost protection on hand.
• The warmest places are low and in the west or southeast. Uravan, Grand Junction and La Junta all have median seasons over 170 days.
• Your garden can differ from the nearest station. Boulder’s in-town station (1,672 m) has a median last freeze of May 6. Boulder 14 W, at 2,996 m in the high mountains about 23 km west of town, has June 21. That’s 1,324 m higher and about six and a half weeks later. Smaller differences count too. A garden in a frost pocket, on a hillside or near a large lake can differ from its station by “a week or more,” as our methodology page puts it.

Every Colorado station

All 210 stations

Flag E (estimated) is explained under “How to read the tables” above. 12 of Colorado’s 210 stations carry it.

FAQ

Planting along the Front Range

When should I plant in Denver?

It depends on the crop. At the Denver Water Dept station, the median last 32°F night is April 30, and the chance of a freeze drops to 10% by May 13. Hardy crops can go in earlier. For tomatoes and other tender crops, Colorado State University Extension says that “planting time along the Colorado Front Range is typically late May.”

When can I plant tomatoes outside in Denver?

Usually late May. CSU Extension says tomatoes need nights above 52°F and days above 60°F at transplant, and that a light frost readily kills them. Our data points the same way. At the Denver Water Dept station, the estimated chance of a 36°F night, when frost is possible, falls to about 10% by May 25.

Is Mother’s Day safe for planting in Colorado?

Not reliably. Mother’s Day fell on May 10 in 2026. At the Denver Water Dept station, the estimated chance of another 32°F night after May 10 is about 16%, and of a 36°F night, when frost is possible, about 43%. Those odds come from our frost odds method. Higher stations are later still.

When is the last frost in Colorado Springs?

At Colorado Springs Muni AP, the median last 32°F night is May 3, and the 10% date is May 15. The median first fall freeze there is October 8.

High country

What can I grow at really high altitude?

Plan for a very short season. A CSU Extension Master Gardener in Gilpin County, writing about gardens over 7,000 feet, says: “We have had frost as late as July and as early as August.” The CSU page recommends short days-to-harvest varieties, raised beds and floating row covers. Our data agrees on the timing. Cochetopa Creek (2,440 m) has a median of just 74 frost-free days.

Sources

• NOAA National Centers for Environmental Information, U.S. Climate Normals 1991-2020, annual/seasonal station normals (fields PRBLST, PRBFST and PRBGSL at 32°F). Station filter and ZIP matching: methodology.
• NOAA NCEI, Readme: By-Variable By-Station Normals Files (completeness flags).
• Colorado State University Extension, Growing Tomatoes. https://extension.colostate.edu/resource/growing-tomatoes/
• CSU Extension Gilpin County, Vegetables that Grow Well Over 7,000′ (Christy Hoyl, Master Gardener). https://gilpin.extension.colostate.edu/programs/mtn-hort/vegetables-over-7000/