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Frost Dates in Colorado
First and last frost dates across Colorado, computed from 111 NOAA weather stations (1991–2020 climate normals). Your exact date depends on your city and microclimate — use the ZIP lookup on the main tool for a station-specific answer.
Last spring frost
May 11
statewide median · range Apr 20–Jun 21
First fall frost
Oct 3
statewide median · range Sep 5–Oct 21
Growing season
145 days
median · range 74–182
Stations used
111
NOAA 1991–2020 normals
Frost dates by city
Median dates from the nearest NOAA station to each city. The "cautious" date is the 10% spring value — planting after it means only a ~10% chance of a later frost.
| City | Nearest station | Last spring frost | First fall frost | Growing season | Safe transplant |
|---|---|---|---|---|---|
| Denver | Denver-Stapleton · 7 mi | May 4 (cautious: May 16) | Oct 8 | 156 days | May 18 |
| Colorado Springs | Colorado Springs Muni Ap · 7 mi | May 3 (cautious: May 15) | Oct 8 | 158 days | May 17 |
| Fort Collins | Ft Collins · 1 mi | May 2 (cautious: May 14) | Oct 7 | 157 days | May 16 |
How frost varies across Colorado
Spring frost timing spans about 62 days across the state. Gateway in Colorado typically sees its last spring frost around April 20, while Cochetopa Creek in Colorado doesn't clear frost until about June 21. Within any city, low spots and valleys run colder than the station average; areas near buildings and pavement run warmer.
When to plant in Colorado
As a rule of thumb, cool-season crops (lettuce, peas, spinach) can go in 2–4 weeks before your last spring frost; warm-season transplants (tomatoes, peppers) should wait about 2 weeks after it — around May 25 for the statewide median. Check your city's row above rather than the statewide median: a 62-day statewide spread makes the city-level date the one that matters.
These are climate normals (what's typical), not forecasts. For the current year, watch the 10-day forecast around your planting date.
How this is computed
Statewide medians are the median of the 111 NOAA stations' median frost dates — half the stations run earlier, half later. City rows use the nearest station with 30-year freeze records. Dates are 32°F freeze probabilities from NOAA NCEI 1991–2020 U.S. Climate Normals; nothing is estimated or interpolated.
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Frequently asked questions
When is the last frost date in Colorado?
The statewide median last spring frost is May 11, but it ranges from April 20 to June 21 depending on where in the state you are. Use your city's row in the table above, or the ZIP lookup on the main tool, for a station-specific date.
When can I plant tomatoes outside in Colorado?
Warm-season transplants like tomatoes should wait about two weeks after your last spring frost — around May 25 for the statewide median. Your city may differ by weeks; check the "safe transplant" column in the city table.
How long is the growing season in Colorado?
The median growing season across 111 NOAA stations is 145 days, ranging from 74 to 182 days by location.
Why do frost dates vary so much within Colorado?
Frost timing follows latitude, elevation, and local terrain. Across Colorado, last spring frost dates span about 62 days — from around April 20 near Gateway to June 21 near Cochetopa Creek. Microclimates (low spots, valleys, urban heat) shift dates further at the garden level.
Where does this data come from?
All frost dates are computed from the NOAA National Centers for Environmental Information 1991–2020 U.S. Climate Normals freeze data (public domain), using each station's 32°F freeze probability statistics. No dates are estimated or interpolated.