Commerce City, Colorado Frost Dates, Growing Season & Hardiness Zone
Frost odds and planting zone for Commerce City for the 2027 season, based on 1991–2020 normals.
Last frost date
May 3
typical (50% chance of a later 32°F night)
Safer date: May 16 (10% risk)
earlyMay 3
typicalMay 16
safer
First fall frost
Oct 7
typical (50% chance it has happened by then)
Early-risk date: Sep 26 (10%)
Growing season
155 days
typical frost-free (32°F) season
Short year: 138 days (1 year in 10 is shorter)
USDA hardiness zone
5b
2023 map: -15 to -10°F average coldest night
2012 map: 5b
Stations around the metro don't all agree. The typical last frost is as early as Apr 30 at Denver Water Dept. and as late as May 7 at Cherry Creek Dam.
Typical last freeze (32°F): May 3. In 1 year out of 10, the last one comes after May 16.
Based on NOAA station Brighton 3 SE (USC00050950), 4.7 mi NNW, elevation 5,016 ft (−162 ft vs. city center). Confidence: High.
When is the last frost in Commerce City?
In half of years, the last 32°F night has passed by May 3. In 1 year out of 10, one still comes after May 16. The last 36°F night (frost possible on plants) typically comes later, around May 13, and the last 28°F hard freeze earlier, around Apr 23.
The typical date (May 3) and the safer 1-in-10 date (May 16) are 13 days apart. If you plant in between, you're taking a chance; watch the 10-day forecast.
The typical last 36°F night (frost possible on plants in low spots) comes around May 13, 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.
| Threshold | 10% (safer) | 30% | 50% (typical) | 90% (early) |
|---|---|---|---|---|
| 36°F (frost possible on plants) | May 27 | May 18 | May 13 | May 3 |
| 32°F freeze | May 16 | May 8 | May 3 | Apr 22 |
| 28°F hard freeze | May 7 | Apr 30 | Apr 23 | Apr 8 |
All probabilities (10–90%)
| Threshold | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F (frost possible on plants) | May 27 | May 21 | May 18 | May 16 | May 13 | May 11 | May 9 | May 6 | May 3 |
| 32°F freeze | May 16 | May 12 | May 8 | May 6 | May 3 | May 1 | Apr 30 | Apr 27 | Apr 22 |
| 28°F hard freeze | May 7 | May 2 | Apr 30 | Apr 27 | Apr 23 | Apr 20 | Apr 17 | Apr 14 | Apr 8 |
Is it safe to plant after Mother's Day in Commerce City?
Around Commerce City, many gardeners use Mother's Day as their cue to plant (CSU PlantTalk). It falls on May 9 in 2027. From then on, the chance of another 32°F night is between 20% and 30%; for a 36°F night (frost possible on plants) it's about 70% (NOAA 1991–2020, Brighton 3 SE).
Is it too early to plant in Commerce City?
Before May 3 the odds of another 32°F night are better than even; after May 16 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 Commerce City?
The typical first fall freeze (32°F) comes by Oct 7, but 1 year in 10 it shows up as early as Sep 26. Cold 36°F nights (frost possible on plants) typically start around Sep 30, and the first hard freeze (28°F) typically comes around Oct 16.
Fall plantings are timed backward from first frost: Oct 7 typically, or Sep 26 if you want a cushion. See the planting calendar for each crop's date.
| Threshold | 10% (early) | 30% | 50% (typical) | 90% (late) |
|---|---|---|---|---|
| 36°F (frost possible on plants) | Sep 17 | Sep 25 | Sep 30 | Oct 10 |
| 32°F freeze | Sep 26 | Oct 2 | Oct 7 | Oct 19 |
| 28°F hard freeze | Oct 4 | Oct 11 | Oct 16 | Oct 29 |
All probabilities (10–90%)
| Threshold | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F (frost possible on plants) | Sep 17 | Sep 22 | Sep 25 | Sep 28 | Sep 30 | Oct 2 | Oct 4 | Oct 7 | Oct 10 |
| 32°F freeze | Sep 26 | Sep 30 | Oct 2 | Oct 5 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 19 |
| 28°F hard freeze | Oct 4 | Oct 7 | Oct 11 | Oct 14 | Oct 16 | Oct 19 | Oct 22 | Oct 25 | Oct 29 |
How long is Commerce City's growing season?
In a typical year, Commerce City gets 155 days between the last and first 32°F nights. About 1 year in 10, the season is shorter than 138 days.
That's enough time for most warm-season vegetables if they go in on time. Long-season crops do best started from transplants.
Each year the station logs an average of 2,923 growing degree days (base 50°F), a measure of the heat available for crop growth.
| Threshold | 10% (long year) | 50% (typical) | 90% (short year) |
|---|---|---|---|
| 36°F (frost possible on plants) | 152 days | 137 days | 119 days |
| 32°F freeze | 172 days | 155 days | 138 days |
| 28°F hard freeze | 193 days | 174 days | 155 days |
How does Commerce City's season compare?
Among the 20 Colorado cities with frost dates on this site, the typical frost-free season in Commerce City (155 days) is tied for the 11th longest.
Compared with the 56 U.S. cities with frost dates on this site, this typical frost-free season is longer than in 8 and shorter than in 46.
Growing degree days (base 50°F)
Annual normal: 2,923 GDD (NOAA flag S, 25 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):
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 0 | 3 | 29 | 115 | 383 | 932 | 1,679 | 2,360 | 2,778 | 2,902 | 2,922 | 2,923 |
What growing zone is Commerce City? (USDA 2023)
On the 2023 USDA map, Commerce City is zone 5b (-15 to -10°F average coldest winter night). That's no change from the 2012 map.
| ZIP | 2023 | 2012 | Change | Share of ZIP in Commerce City |
|---|---|---|---|---|
| 80601 | 5b | 5b | unchanged | 2% |
| 80603 | 5b | 5b | unchanged | 2% |
| 80640 mostly in city | 5b | 5b | unchanged | 51% |
Other ZIPs touching Commerce City
ZIPs outside the 806 prefix that overlap the city boundary:
- 80022: 2023 6a, 2012 5b (34.0% of the ZIP is in Commerce City)
- 80216: 2023 6a, 2012 5b (1.8% of the ZIP is in Commerce City)
- 80229: 2023 6a, 2012 5b (0.0% of the ZIP is in Commerce City)
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 Commerce City's frost dates?
No. Hardiness zones are based only on the average coldest winter temperature. They say nothing about when spring and fall frosts happen. Commerce City's frost dates come from NOAA's 1991–2020 frost probabilities, which did not change with the 2023 zone map. Use your zone to pick perennials that will survive winter, and your frost dates to time planting.
Why do Commerce City frost dates differ between websites?
You may see May 8 given as Commerce City's last frost date. That's the 30%-risk date, meaning about 3 years in 10 still have a 32°F night after it. Our headline date is May 3, the 50% (median) date.
May 16 is the date we call 'safer': it's the 10%-risk date, with a 32°F night after it in only about 1 year in 10.
You may also see May 13. 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 10 stations within 25 miles of the city center that pass our quality rules give typical (50%) last 32°F frost dates from Apr 30 to May 7; see the table below.
| Date | What it is (NOAA 1991–2020) |
|---|---|
| May 8 | 32°F last frost, 30% risk (a 'balanced' date) |
| May 13 | 36°F last cold night, 50% (frost possible on plants) |
| May 16 | 32°F last frost, 10% risk (the 'safer' date) |
| Apr 23 | 28°F last hard freeze, 50% |
| May 4 | 32°F last frost, 50%, at Denver-Stapleton (nearest station with NOAA flag S) |
| Station | Distance | Elevation | Typical last frost |
|---|---|---|---|
| Denver Water Dept. | 15.5 mi SW | 5,228 ft | Apr 30 |
| Northglenn | 11.6 mi W | 5,407 ft | May 2 |
| Marston Filter Plant | 23.1 mi SW | 5,610 ft | May 2 |
| Brighton 3 SE used here | 4.7 mi NNW | 5,016 ft | May 3 |
| Lakewood | 19.6 mi WSW | 5,640 ft | May 3 |
| Denver-Stapleton | 9.2 mi SSW | 5,286 ft | May 4 |
| Denver International Airport | 8.1 mi ESE | 5,414 ft | May 5 |
| Wheat Ridge 2 | 18.6 mi WSW | 5,398 ft | May 5 |
| Cherry Creek Dam | 17.8 mi S | 5,647 ft | May 7 |
| Longmont 2 ESE | 24.8 mi NW | 4,950 ft | May 7 |
Which weather station is this based on?
- Station
- Brighton 3 SE (NOAA USC00050950, COOP)
- Distance
- 4.7 mi NNW of the city center
- Elevation
- 5,016 ft; city center 5,178 ft (USGS), difference −162 ft
- Record
- NOAA completeness flag S, 25 of 30 years (1991–2020)
- Confidence
- High (rule)
Confidence: High. At 4.7 miles from the city center and only 162 ft off in elevation, with frost statistics that meet our completeness rule (NOAA flag S, 25 of 30 years), this station is a close match.
| Station | ID | Distance | Elev. (Δ) | Last frost 50% | First frost 50% | Season 50% | NOAA flag / years |
|---|---|---|---|---|---|---|---|
| Brighton 3 SE | USC00050950 | 4.7 mi NNW | 5,016 ft (-162) | May 3 | Oct 7 | 155 d | S / 25 |
| Denver International Airport | USW00003017 | 8.1 mi ESE | 5,414 ft (+236) | May 5 | Oct 9 | 156 d | R / 25 |
| Denver-Stapleton | USW00023062 | 9.2 mi SSW | 5,286 ft (+108) | May 4 | Oct 8 | 156 d | S / 28 |
| Northglenn | USC00055984 | 11.6 mi W | 5,407 ft (+229) | May 2 | Oct 11 | 160 d | S / 26 |
| Denver Water Dept. | USC00052223 | 15.5 mi SW | 5,228 ft (+50) | Apr 30 | Oct 12 | 165 d | R / 22 |
| Cherry Creek Dam | USC00051547 | 17.8 mi S | 5,647 ft (+469) | May 7 | Oct 8 | 152 d | R / 13 |
| Wheat Ridge 2 | USC00058995 | 18.6 mi WSW | 5,398 ft (+220) | May 5 | Oct 5 | 151 d | S / 28 |
| Lakewood | USC00054762 | 19.6 mi WSW | 5,640 ft (+462) | May 3 | Oct 7 | 155 d | R / 24 |
| Marston Filter Plant | USC00055402 | 23.1 mi SW | 5,610 ft (+432) | May 2 | Oct 11 | 160 d | R / 18 |
| Longmont 2 ESE | USC00055116 | 24.8 mi NW | 4,950 ft (-228) | May 7 | Oct 5 | 151 d | R / 17 |
Other stations within 25 mi (not used)
- Denver Centennial Airport (USW00093067), 21.8 mi S, 5,883 ft: typical last frost May 5. Not used: |elev diff| 705 ft > 500 ft.
- Ralston Reservoir (USC00056816), 23.6 mi W, 5,900 ft: typical last frost May 3. Not used: |elev diff| 722 ft > 500 ft.
65 other NOAA normals stations within 40 km (mostly rain gauges) have no frost statistics.
Commerce City planting dates at a glance
Balanced dates use the 30%-risk last-frost date as the anchor. The Commerce City planting calendar has typical and safe dates, fall planting and a month-by-month list for 27 vegetables.
| Crop | Start indoors | Plant outdoors (balanced) | Fall |
|---|---|---|---|
| Tomatoes | Apr 26 – May 10 | Jun 14 | – |
| Peppers | Mar 27 – Apr 10 | May 22 | – |
| Potatoes | – | Apr 24 – May 8 | – |
| Onions (dry, from sets) | – | Apr 10–24 | – |
| Peas | – | Apr 10–24 | sow by Jul 20 |
| Lettuce (leaf) | – | Apr 10–24 | sow by Jul 25 |
| Carrots | – | Apr 24 – May 8 | sow by Jul 15 |
| Beans (snap) | – | May 8 | sow by Jul 11 |
| Summer squash | – | May 8 | sow by Jul 21 |
| Broccoli | Feb 20 – Mar 6 | Apr 10–24 | transplant by Jul 20 |
| Cabbage | Feb 20 – Mar 6 | Apr 10–24 | transplant by Jun 30 |
| Cauliflower | Mar 6–20 | Apr 24 – May 8 | – |
| Kohlrabi | – | Apr 10–24 | sow by Aug 4 |
| Green onions | – | Apr 10–24 | sow by Jul 25 |
| Radishes | – | Apr 10–24 | sow by Aug 24 |
| Spinach | – | Apr 10–24 | sow by Aug 14 |
| Turnips | – | Apr 10–24 | sow by Aug 4 |
| Beets | – | Apr 24 – May 8 | sow by Jul 25 |
| Swiss chard | – | Apr 24 – May 8 | sow by Jul 25 |
| Parsnips | – | Apr 24 – May 8 | – |
| Sweet corn | – | May 8 | – |
| Cucumbers | – | May 8 | sow by Jul 16 |
| Eggplant | Mar 20 – Apr 10 | May 22 | – |
| Cantaloupe | – | May 22 | – |
| Watermelon | – | May 22 | – |
| Winter squash | – | May 22 | – |
| Garlic | – | – | plant Oct 1–14 |
When to plant tomatoes in Commerce City · Fall planting dates for Commerce City
Frost dates near Commerce City
| City | Distance | Last frost | First frost | Season | Zone 2023 |
|---|---|---|---|---|---|
| Thornton frost dates | 8 mi | May 2 | Oct 11 | 160 days | 6a |
| Aurora frost dates | 13 mi | May 7 | Oct 8 | 152 days | 6a |
| Denver frost dates | 14 mi | Apr 30 | Oct 12 | 165 days | 6a |
| Arvada frost dates | 19 mi | May 5 | Oct 5 | 151 days | 6a |
| Centennial frost dates | 20 mi | May 5 | Oct 8 | 154 days | 6a |
| Lakewood frost dates | 21 mi | May 3 | Oct 7 | 155 days | 6a |
Frequently asked questions
What is the average last frost date in Commerce City?
Based on NOAA 1991–2020 normals at Brighton 3 SE, Commerce City's typical last 32°F night is May 3. That's the median (50%) date. For a safer target, go with May 16, after which a freeze comes in only about 1 year in 10.
When is the first frost in Commerce City?
The first 32°F night typically arrives by Oct 7. About 1 year in 10, it comes as early as Sep 26. A 36°F night (frost possible on plants) typically shows up around Sep 30.
What growing zone is Commerce City, Colorado? Is Commerce City zone 5 or 6?
Commerce City is in USDA hardiness zone 5b on the current 2023 map (zone 5 for short). On the older 2012 map, most of the city was 5b. That's why older references still say 'zone 5'.
What growing zone is Commerce City, Colorado?
Commerce City is in USDA hardiness zone 5b on the 2023 map, the same as on the 2012 map.
Is it too early to plant in Commerce City?
If it's before May 3, it's too early for frost-tender plants: another 32°F night is more likely than not. From May 3 to May 16, the risk falls from 50% to 10%. Cool-season crops such as peas and lettuce can be planted 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 quite. A freeze is when the air reaches 32°F. Frost is ice that forms on surfaces, and on calm, clear nights it can form with the air a few degrees above freezing. So in Commerce City, the first 36°F night (frost possible on plants) typically comes around Sep 30, before the first 32°F night (Oct 7).
Download & sources
- Add Commerce City 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 USC00050950); 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.