Frost dates · USDA zone 5b
Frost dates for Windsor, CO
Windsor, CO sees its last 32 °F night of spring around May 3 and its first of fall around October 6 — a 154-day freeze-free season in a typical year.
Pick a sauce; the Plan Builder runs this station's dates and hands back the calendar, plant count and gear list.
Freeze odds, by date
| Odds | Last spring freeze after | First fall freeze before |
|---|---|---|
| 9 years in 10 | Apr 21 | Oct 17 |
| Median — 1 year in 2 | May 3 | Oct 6 |
| 1 year in 10 | May 15 | Sep 22 |
The top row is the risky edge: in 9 years of 10 a spring freeze still comes after it, so tender transplants set out then need cover. The bottom row is the cautious date — only 1 year in 10 freezes after it — and the one to plan uncovered tender transplants against. Freeze-free season: 154 days median, at least 135 in 9 years of 10, at least 171 days in 1 year of 10. NOAA ranks season length year by year, so it is not the gap between two rows above. A hard freeze (28 °F) has a median last date of Apr 23 and first of Oct 14.
Windsor planting calendar, 2027
Every row runs from the median last frost (May 3) and median first frost (Oct 6) above, using each cultivar's days to maturity. Same engine as the Plan Builder.
| Crop | Start indoors | Transplant / plant | First harvest | Days |
|---|---|---|---|---|
| Hardneck GarlicSiberian (porcelain hardneck) | — | Oct 15prior fall | Jun 12 | 240 from sow |
| Spanish OnionYellow Sweet Spanish (long-day) | Feb 8 | Apr 5 | Jul 24 | 110 from transplant |
| Mustard greensGarnet Giant (Brassica juncea) | Direct sow | May 3 | Jun 2 | 30 from sow |
| CilantroSlow Bolt (Coriandrum sativum) | Apr 19 | Apr 19 | Jun 3 | 45 from sow |
| Genovese BasilGenovese | Apr 5 | May 17 | Jul 16 | 60 from transplant |
| CayenneLong Slim Cayenne (Capsicum annuum) | Mar 8 | May 10 | Jul 24 | 75 from transplant |
| HabaneroOrange Habanero (Capsicum chinense) | Feb 22 | May 17 | Aug 20 | 95 from transplant |
| JalapeñoEarly Jalapeño (Capsicum annuum) | Mar 8 | May 10 | Jul 24 | 75 from transplant |
| Marconi Red PepperMarconi Red (Capsicum annuum) | Mar 8 | May 10 | Jul 29 | 80 from transplant |
| SerranoSerrano Tampiqueño (Capsicum annuum) | Mar 8 | May 10 | Jul 29 | 80 from transplant |
| Nantes CarrotScarlet Nantes | Apr 19 | Apr 19 | Jun 28 | 70 from sow |
| TomatilloToma Verde | Mar 22 | May 10 | Jul 19 | 70 from transplant |
| Roma TomatoRoma VF (determinate paste) | Mar 22 | May 10 | Jul 24 | 75 from transplant |
| San Marzano TomatoSan Marzano (indeterminate paste) | Mar 22 | May 10 | Jul 29 | 80 from transplant |
Tight means first harvest lands within two weeks of the median first fall frost: start that crop indoors on time or cover it in fall.
What sauce can Windsor grow?
Each sauce, scheduled for a Windsor container garden: when the first seeds go in and when enough fruit has ripened for one batch.
Windsor frost questions
When is the last frost in Windsor, CO?
The median last 32 °F freeze at FT COLLINS 4 E, CO is May 3: half of years see a later one. One year in ten, a freeze still comes after May 15; nine years in ten, it comes after April 21. Source: NOAA NCEI 1991–2020 U.S. Climate Normals.
When is the first frost in Windsor, CO?
The median first 32 °F freeze of fall is October 6. One year in ten it arrives before September 22; nine years in ten, before October 17.
How long is the growing season in Windsor, CO?
154 days between the last spring and first fall 32 °F freeze in a median year. Nine years in ten the season runs at least 135 days; one year in ten, at least 171 days.
What growing zone is Windsor, CO?
USDA hardiness zone 5b, per the 2023 USDA Plant Hardiness Zone Map for ZIP 80550. A zone describes the coldest winter night, not when frost ends, so it is the wrong number for a planting calendar — the frost dates on this page are the right one.
When should I plant tomatoes in Windsor, CO?
Start Roma VF (determinate paste) seeds indoors around Mar 22 and transplant around May 10, 1 week after the median last frost. To cut the freeze risk to one year in ten, wait for May 15. First ripe fruit lands around Jul 24.
When should I plant peppers in Windsor, CO?
Sow jalapeño indoors on a heat mat around Mar 8; transplant no earlier than May 10, and wait past it until nights hold above 50 °F — that can run weeks later. First green pods around Jul 24.
Nearby in Colorado
- Greeleylast frost May 2
- Lovelandlast frost May 3
- Fort Collinslast frost May 3
- Longmontlast frost May 7
- Brightonlast frost May 3
- Boulderlast frost May 6
All Colorado frost dates → · How frost-date math drives a sowing calendar →