Centennial, Colorado Frost Dates, Growing Season & Hardiness Zone

When is the last frost in Centennial?

In half of years, the last 32°F night has passed by May 5. In 1 year out of 10, one still comes after May 17. The last 36°F night (frost possible on plants) typically comes later, around May 15, and the last 28°F hard freeze earlier, around Apr 25.

Planting between the typical date (May 5) and the safer 1-in-10 date (May 17) is a bet. Over those 12 days, let the 10-day forecast guide you.

The typical last 36°F night (frost possible on plants in low spots) comes around May 15, 10 days after the typical last 32°F night. On clear, calm nights, frost can form on leaves even when the thermometer reads above freezing.

Is it safe to plant after Mother's Day in Centennial?

Mother's Day is the usual planting signal for many gardeners around Centennial (CSU PlantTalk). In 2027 that's May 9. As of that date, NOAA 1991–2020 normals at Denver Centennial Airport give between 30% and 40% odds of another 32°F night and between 70% and 80% odds of another 36°F night (frost possible on plants).

Is it too early to plant in Centennial?

Before May 5 the odds of another 32°F night are better than even; after May 17 they are about 1 in 10 or less.

Today's risk is computed in your browser from the same NOAA probability table, shown as the range between the two nearest NOAA probability levels.

When is the first frost in Centennial?

By Oct 8, half of years have had their first 32°F night. In 1 year out of 10, it comes as early as Sep 25. In a typical year, look for the first 36°F night (frost possible on plants) around Oct 1 and the first 28°F hard freeze around Oct 17.

For fall crops, count back from Oct 8, or from Sep 25 to be safe. Our planting calendar does the math for each crop.

How long is Centennial's growing season?

In a typical year, Centennial gets 154 days between the last and first 32°F nights. About 1 year in 10, the season is shorter than 135 days.

A season this long fits most warm-season vegetables planted on time. Long-season crops do best when started from transplants.

Each year the station logs an average of 2,708 growing degree days (base 50°F), a measure of the heat available for crop growth.

How does Centennial's season compare?

Of the 20 Colorado cities with frost dates on this site, Centennial has a typical frost-free season of 154 days, which is the 13th longest.

Compared with the 56 U.S. cities with frost dates on this site, this typical frost-free season is longer than in 7 and shorter than in 48.

Growing degree days (base 50°F)

Annual normal: 2,708 GDD (NOAA flag R, 19 years). Running total by the end of each month (sum of NOAA daily GDD normals, so the year-end total can differ slightly from the annual normal):

What growing zone is Centennial? (USDA 2023)

Centennial is in USDA zone 6a on the 2023 map, which means an average coldest winter night of -10 to -5°F. Most of the city was 5b on the 2012 map, and 4 of 4 city ZIPs found in both tables moved up half a zone.

Zones: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed 2026-10-08. Shown as published in the ZIP tables; this page does not show a zone map. Not the official USDA Plant Hardiness Zone Map (official map: planthardiness.ars.usda.gov).

Does the new zone change Centennial's frost dates?

No. Zones describe only how cold the coldest winter night gets on average. They don't tell you when frost starts or stops. The frost dates for Centennial come from NOAA's 1991–2020 frost probabilities, which the 2023 zone map left untouched. Choose winter-hardy perennials by zone, and schedule planting by frost dates.

Why do Centennial frost dates differ between websites?

If you've seen May 10 listed as Centennial's last frost date, that's the 30%-risk date: about 3 years in 10 still get a 32°F night after it. We lead with May 5, the 50% (median) date.

The 'safer' date, May 17, is the 10%-risk date. A 32°F night after it happens in only about 1 year in 10.

You may also see May 15. That's the 50% date for a 36°F night (frost possible on plants) rather than a 32°F freeze, so sites using 36°F as their cutoff list later dates.

The choice of weather station matters too. The 13 stations within 25 miles of the city center that pass our quality rules give typical (50%) last 32°F frost dates from May 2 to May 16; see the table below.

Which weather station is this based on?

Station

Denver Centennial Airport (NOAA USW00093067, WBAN/ASOS-AWOS)

Distance

1.6 mi SSE of the city center

Elevation

5,883 ft; city center 5,740 ft (USGS), difference +143 ft

Record

NOAA completeness flag R, 20 of 30 years (1991–2020)

Confidence

High (rule)

Confidence: High. The station is 1.6 miles from the city center, only 143 ft different in elevation, and its frost statistics meet our completeness rule (NOAA flag R, 20 of 30 years).

Caveat: these frost statistics carry NOAA's 'R' (representative) flag. They're based on 20 of the 30 years in 1991–2020, with missing months filled in from surrounding stations. The nearest station with a full 'S' (standard) record is Denver-Stapleton, 11.9 mi away, with a typical last frost of May 4.

Centennial planting dates at a glance

Balanced dates use the 30%-risk last-frost date as the anchor. The Centennial planting calendar has typical and safe dates, fall planting and a month-by-month list for 27 vegetables.

When to plant tomatoes in Centennial · Fall planting dates for Centennial

Frost dates near Centennial

All Colorado cities

Frequently asked questions

What is the average last frost date in Centennial?

May 5 is the median (50%) date for Centennial's last 32°F night, from NOAA 1991–2020 normals at Denver Centennial Airport. To play it safe, use May 17: only about 1 year in 10 has a freeze after it.

When is the first frost in Centennial?

The first 32°F night typically arrives by Oct 8. About 1 year in 10, it comes as early as Sep 25. A 36°F night (frost possible on plants) typically shows up around Oct 1.

What growing zone is Centennial, Colorado? Is Centennial zone 5 or 6?

Centennial is in USDA hardiness zone 6a on the current 2023 map (zone 6 for short). On the older 2012 map, most of the city was 5b. That's why older references still say 'zone 5'.

Is it too early to plant in Centennial?

For frost-tender plants, yes if it's before May 5: until then, the odds of another 32°F night are better than even. Between May 5 and May 17, the risk falls from 50% to 10%. Cool-season crops like peas and lettuce can go in weeks earlier; see the planting calendar.

What temperature is a killing frost?

A light frost is enough to kill tender crops such as tomatoes. CSU Extension describes 28–32°F as a light frost and anything below 28°F as a heavy frost. We report NOAA odds at three thresholds: 36°F (frost possible on plants), 32°F (freeze, our headline) and 28°F (hard freeze).

Is first frost the same as first freeze?

Not exactly. A freeze is about the air reaching 32°F. Frost is ice on surfaces, which can form on calm, clear nights while the air is still a few degrees above freezing. So in Centennial, the first 36°F night (frost possible on plants) typically comes around Oct 1, ahead of the first 32°F night (Oct 8).

Download & sources

• Add Centennial frost & planting dates to your calendar (.ics, 2027)
• Printable planting calendar (PDF)
• How these numbers are calculated

Data: NOAA NCEI U.S. Climate Normals 1991–2020 (annual/seasonal and daily normals, station USW00093067); USDA Plant Hardiness Zone ZIP tables 2023 and 2012 by the PRISM Group, Oregon State University; Census 2020 ZIP/place relationship file; USGS elevation. Long-term odds, not a forecast. Figures and sentences are generated from these data by fixed rules; see the methodology. Last updated 2026-10-08.