Denver, CO Frost Dates: Last Spring and First Fall Frost

Frost leaves Denver on May 4 and comes back on October 8 when the odds are even, a window of 156 days for tender plants.

Put May 16 and September 25 on the calendar as well. A spring freeze after the first of them, or a fall freeze before the second, happens in only one year out of ten, so those dates cover nine years in ten. Against the 100-city median of 229 days, Denver has 73 days less room before frost returns.

Behind every date on this page is one weather station, Denver-Stapleton (NOAA USW00023062), 0.6 miles east of Denver's internal point in the Census Bureau's files and about 5,300 feet up.

Last spring frost in Denver

One year in ten has a freeze on or after May 16. In nine years out of ten there is still a freeze on or after April 20, and half of years see one on or after May 4.

Only 26 days separate the earliest and latest of these dates, a tighter run than most of the 100 cities here, so the typical date is a fairly dependable guide in Denver.

First fall frost in Denver

NOAA's early fall date for Denver is September 25, its even-odds date is October 8 and its late date is October 20; the first freeze has come by each of them in one, five and nine years out of ten.

Fall frost keeps to a tight calendar in Denver: 25 days from the 10% date to the 90% date, less than in most of the 100 cities here.

How long is the frost-free season in Denver?

With a season well short of the middle of these pages, Denver leaves little time for slow crops, as the planting dates below show. A short year costs just 18 days against a typical one (138 days against 156 days), so a season-length plan for Denver holds up in most years.

These figures are NOAA's own counts of freeze-free days across its simulated years, which is why they can differ a little from the days between the two typical dates. A night at or below 32°F happens in 100% of years at this station, so frost is a yearly event here.

Hard freeze dates for Denver

A hard freeze follows the first frost quickly in Denver: the typical 28°F night arrives on October 18 in fall, only 10 days after the first 32°F one on October 8, and in spring the last one comes on April 22, 12 days before the last 32°F frost. Tender plants get little warning here. The late 28°F spring date, May 7, is the one that still catches blooms and young transplants one year in ten, and the early fall date, October 3, is when a hard freeze has arrived in one fall out of ten.

Using Denver's frost dates in the garden

In Denver the University of New Hampshire Extension count lands like this, measured from the typical last frost on May 4: lettuce from April 6 to April 13, cabbage on April 6, seed potatoes from April 20 to April 27, then peppers on May 18 and beans from May 4. The University of New Hampshire Extension sheet gives peas no frost count at all; sow them as soon as the soil thaws.

The late date comes 12 days after the typical one; choose it for plants you cannot cover.

Denver's first frost leaves room for only 20 of the 34 fall crops, counting back NC State Extension's days to harvest and University of Georgia Extension's harvest allowance of 18 days; for the other 14 the last planting day falls before July. The slowest crop that still fits is cauliflower, which needs 83 days before the early first frost and so must be in by July 4.

Worked example: a tomato plan for Denver

A gardener in Denver who follows University of New Hampshire Extension sets tomato transplants out one to two weeks after the last frost: May 11 to May 18 from the typical date of May 4, or May 23 to May 30 from the late date of May 16, 12 days later.

Seeds start six to eight weeks before the set-out day, so counting back from the first day of the late window gives March 28 to April 11 for sowing indoors.

From the last set-out day to the early first frost on September 25 is 118 days. NC State Extension gives 75 to 85 days, and the longer figure still fits with 33 days to spare.

Where Denver's numbers are measured

The station is 0.6 miles east of the Census Bureau's internal point for Denver, close enough that its record is the natural reference for the city.

Its elevation is about 5,300 feet. Of the 100 stations behind these pages, 2 sit higher and 97 lower. NOAA flags this station's record as standard, the code S, for the data behind its 50% last-frost value.

The Census Gazetteer gives no elevation for Denver itself, so this page cannot tell you whether your garden sits above or below the station. If it is noticeably higher or lower, compare the stations the frost dates tool lists nearby and lean toward the colder reading.

How Denver's frost dates compare

The closest city on these pages is Aurora, CO, 9.3 miles away. The next two are farther afield, so read them as a wider look at the region.

• Aurora, CO lies 9.3 miles south-east of Denver. Typical last frost May 7, first frost October 8, 152 days between; its last frost falls within a few days of Denver's, and the season is within about a week of Denver's.
• Colorado Springs, CO, 62 miles to the south: last frost May 3, first frost October 8, 158 days frost-free; its last frost is nearly the same as Denver's, and the season is about the same length as Denver's.
• Albuquerque, NM (336 miles, south): its last frost comes 19 days before Denver's, and the season runs 37 days longer. Its typical dates are April 15 and October 27, with 193 days frost-free.

Take these dates further

The frost dates tool opens on this station and lists every probability date, not just the ones above. From there, the spring planting planner and fall planting planner turn the dates into crop lists for Denver, and the hardiness zone lookup answers what will overwinter.

Every city covered is on the city frost dates index, sorted by state.

Where these numbers come from

The frost and freeze dates are NOAA's U.S. Climate Normals for 1991–2020 (doi:10.25921/4ek7-fk11), copied from the station's own record without adjustment; NOAA's documentation defines each probability. The city and its internal point come from the Census Bureau's 2024 Gazetteer of places, and the ranking by size from the Census Bureau's Vintage 2024 city and town population estimates, which put Denver at 729,019 people.

The planting dates apply the count rules in University of New Hampshire Extension, NC State Extension and University of Georgia Extension to this station's dates, with nothing added. The methodology page explains how each figure is checked.

These dates describe odds over many years, not next week's weather. Look at the forecast before you plant, and keep a sheet or row cover ready for a night that does not follow the odds.