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

The last spring frost in Aurora, CO comes on May 7 in a typical year, and the first fall frost follows on October 8, leaving a frost-free season of 152 days.

Dates at even odds leave half of all years unprotected. The safer pair for Aurora is May 21 in spring, which only one year in ten passes, and September 25 in fall, which one year in ten arrives before. Among the 100 cities covered here, whose median season is 229 days, Aurora ranks 99th for length and falls 77 days below the middle.

These dates come from the NOAA weather station Cherry Creek Dam (ID USC00051547), 8.3 miles south-west of the Census Bureau's internal point for Aurora, at about 5,650 feet above sea level.

Aurora's last spring frost, by chance

NOAA gives April 26 as the date a spring freeze is still ahead in nine years out of ten, May 7 as the date it is still ahead in half of them, and May 21 as the date only one year in ten passes.

Only 25 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 Aurora.

When is the first frost in Aurora?

Expect the first freeze of fall by October 8 in a typical year. One year in ten brings it by September 25, and nine in ten have had it by October 19.

The early and late fall dates are only 24 days apart, a narrow band next to most cities here, so the first freeze keeps close to its schedule in Aurora.

How long is the frost-free season in Aurora?

With a season well short of the middle of these pages, Aurora leaves little time for slow crops, as the planting dates below show. Seasons here barely vary: the typical year gives 152 days and a short one still gives 133 days, only 19 days less, a steadier record than most cities on these pages.

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. At Cherry Creek Dam a night at or below 32°F turns up in 100% of years, which means these dates apply every winter.

When a hard freeze reaches Aurora

The two freezes sit close together here. The typical hard freeze reaches Aurora on October 15, 7 days after the first frost, and ends on April 29, 8 days ahead of the last. The late 28°F spring date, May 10, is the one that still catches blooms and young transplants one year in ten, and the early fall date, September 30, is when a hard freeze has arrived in one fall out of ten.

What this means for planting in Aurora

In Aurora the University of New Hampshire Extension count lands like this, measured from the typical last frost on May 7: lettuce from April 9 to April 16, cabbage on April 9, seed potatoes from April 23 to April 30, then peppers on May 21 and beans from May 7. The University of New Hampshire Extension sheet gives peas no frost count at all; sow them as soon as the soil thaws.

From the late date, May 21, every tender crop moves back 14 days; that buys protection against a spring only one year in ten brings.

Fall crops are counted back from the first frost, using NC State Extension's days to harvest plus University of Georgia Extension's harvest allowance of 18 days. In Aurora only 20 of the 34 crops in the fall planner have a last planting day in July or later, and the other 14 would have to go in before then, in spring or early summer. Of the crops that fit, cauliflower is the slowest: 83 days from planting to the early frost, which makes July 4 its last day.

Worked example: a tomato plan for Aurora

Take tomatoes in Aurora. The University of New Hampshire Extension rule is to set transplants out one to two weeks after the last frost. From May 7, the typical date, that means May 14 to May 21; from May 21, the late date, it means May 28 to June 4, a delay of 14 days.

Indoors, tomato seeds go in six to eight weeks ahead of set-out; from the first day of the late window that is April 2 to April 16.

From the last set-out day to the early first frost on September 25 is 113 days. NC State Extension gives 75 to 85 days, and the longer figure still fits with 28 days to spare.

About the Cherry Creek Dam station

At 8.3 miles south-west, the station is some distance from Aurora, so parts of the city may not match its record.

NOAA lists it at about 5,650 feet, higher than 98 and lower than 1 of the 100 stations in this set. In NOAA's file the record is marked R, meaning representative.

Because the Census file has no elevation for Aurora, we cannot say how far your yard is above or below this station. When yours is clearly higher or lower, open the nearby stations in the frost dates tool and favor the colder one.

How Aurora's frost dates compare

Denver, CO is a short hop at 9.3 miles; the other two cities below are farther out, so the list moves from local to regional.

• Denver, CO lies 9.3 miles north-west of Aurora. Typical last frost May 4, first frost October 8, 156 days between; spring frost ends about when it does in Aurora, and the season is within about a week of Aurora's.
• Colorado Springs, CO lies 58 miles south of Aurora. Typical last frost May 3, first frost October 8, 158 days between; the last frost is 4 days earlier than in Aurora, and the season is about the same length as Aurora's.
• Albuquerque, NM, 335 miles to the south: last frost April 15, first frost October 27, 193 days frost-free; spring frost ends 22 days sooner than in Aurora, and it has 41 days more without frost.

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 Aurora, and the hardiness zone lookup answers what will overwinter.

Looking for another city? The city frost dates index lists every page, grouped 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. Aurora and its internal point are listed in the Census Bureau's 2024 Gazetteer of places; its place in the ranking comes from the Vintage 2024 population estimates, which count 403,130 residents.

University of New Hampshire Extension, NC State Extension and University of Georgia Extension supply the planting rules; this page only counts them from the station's dates. Our methodology describes the tests behind every number.

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.