Last frost date in Windsor, CO
The average last frost in Windsor is May 3. By May 15 the chance of another 32°F night drops to 1 in 10. The first fall frost usually arrives about October 6, which leaves 154 frost-free days. An early freeze before September 22 happens one year in ten.
- Safe after (10% risk)
- May 15
- Average first frost
- Oct 6
- Frost-free season
- 154 days
- Hard freeze (28°F) ends
- Apr 23
Frost likely Mon night, low 32°F
National Weather Service forecast, updated Oct 22, 12:57 UTC
- ThuOct 2249°
- FriOct 2346°
- SatOct 2438°
- SunOct 2536°possible frost
- MonOct 2632°frost
- TueOct 2733°possible frost
- WedOct 2835°possible frost
Planting calendar for Windsor
Windows count forward or back from the average frost dates above. Click a crop for dates across Colorado.
TomatoesMay 10–May 24
PumpkinsMay 17–May 31
SunflowersMay 3–May 24
CucumbersMay 17–May 24
CornMay 10–May 24
Sweet potatoesMay 24–Jun 7
WatermelonMay 17–May 31
Green beansMay 10–May 31
ZucchiniMay 10–May 24
OkraMay 24–Jun 7
PeppersMay 17–May 31
BasilMay 10–May 24
Butternut squashMay 10–May 24
CantaloupeMay 17–May 31
EggplantMay 17–May 31
PotatoesApr 5–Apr 19
OnionsMar 22–Apr 12
CarrotsApr 12–May 17
LettuceApr 19–May 10
BroccoliApr 5–Apr 19
BeetsApr 5–May 17
PeasMar 22–Apr 5
CabbageApr 5–Apr 19
RadishesMar 29–May 10
Brussels sproutsApr 19–May 3
SpinachMar 22–Apr 12
CilantroApr 19–May 10
KaleApr 5–Apr 19
Collard greensApr 5–Apr 19
TurnipsApr 5–Apr 19
DillMay 3–May 17
CeleryMay 10–May 17
CauliflowerApr 19–May 3
LeeksApr 19–May 3
Swiss chardApr 19–May 17
ParsleyApr 19–May 10
Tulip bulbsSep 22–Oct 27
GarlicSep 15–Oct 20
Daffodil bulbsSep 8–Oct 20
StrawberriesApr 5–Apr 19
AsparagusApr 5–Apr 19Frost probabilities
| Threshold | Spring, 90% chance later | Spring, 50% | Spring, 10% | Fall, 10% chance earlier | Fall, 50% | Fall, 90% |
|---|---|---|---|---|---|---|
| Light frost, 32°F | Apr 21 | May 3 | May 15 | Sep 22 | Oct 6 | Oct 17 |
| Hard freeze, 28°F | Apr 8 | Apr 23 | May 8 | Sep 30 | Oct 14 | Oct 26 |
Read the spring 10% column as the date after which only one year in ten still gets frost. That is the safer date for tomatoes, peppers and basil.
Where these numbers come from
NOAA station Fort Collins 4 E (USC00053006) sits 8.8 miles from the center of Windsor at 4,920 feet. Its averages cover 1991 to 2020. Low spots, valleys and open fields can keep getting frost a week or two after the station stops; city centers and lakeshores usually get less of it.
Questions
When is the last frost in Windsor, CO?
The average last frost date in Windsor is May 3, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 15.
When is the first frost in Windsor?
The first frost in fall usually comes around October 6. One year in ten it arrives before September 22.
How long is the growing season in Windsor?
About 154 days between the average last and first frost.
When should I plant tomatoes in Windsor?
Plant tomato seedlings outside from May 10 to May 24. Start seeds indoors six to eight weeks earlier.