Last frost date in Firestone, CO
The average last frost in Firestone is May 7. By May 22 the chance of another 32°F night drops to 1 in 10. The first fall frost usually arrives about October 5, which leaves 151 frost-free days. An early freeze before September 23 happens one year in ten.
- Safe after (10% risk)
- May 22
- Average first frost
- Oct 5
- Frost-free season
- 151 days
- Hard freeze (28°F) ends
- Apr 28
Frost possible in low spots Mon night, low 34°F
National Weather Service forecast, updated Oct 22, 12:57 UTC
- ThuOct 2251°
- FriOct 2347°
- SatOct 2439°
- SunOct 2537°
- MonOct 2634°possible frost
- TueOct 2735°possible frost
- WedOct 2836°possible frost
Planting calendar for Firestone
Windows count forward or back from the average frost dates above. Click a crop for dates across Colorado.
TomatoesMay 14–May 28
PumpkinsMay 21–Jun 4
SunflowersMay 7–May 28
CucumbersMay 21–May 28
CornMay 14–May 28
Sweet potatoesMay 28–Jun 11
WatermelonMay 21–Jun 4
Green beansMay 14–Jun 4
ZucchiniMay 14–May 28
OkraMay 28–Jun 11
PeppersMay 21–Jun 4
BasilMay 14–May 28
Butternut squashMay 14–May 28
CantaloupeMay 21–Jun 4
EggplantMay 21–Jun 4
PotatoesApr 9–Apr 23
OnionsMar 26–Apr 16
CarrotsApr 16–May 21
LettuceApr 23–May 14
BroccoliApr 9–Apr 23
BeetsApr 9–May 21
PeasMar 26–Apr 9
CabbageApr 9–Apr 23
RadishesApr 2–May 14
Brussels sproutsApr 23–May 7
SpinachMar 26–Apr 16
CilantroApr 23–May 14
KaleApr 9–Apr 23
Collard greensApr 9–Apr 23
TurnipsApr 9–Apr 23
DillMay 7–May 21
CeleryMay 14–May 21
CauliflowerApr 23–May 7
LeeksApr 23–May 7
Swiss chardApr 23–May 21
ParsleyApr 23–May 14
Tulip bulbsSep 21–Oct 26
GarlicSep 14–Oct 19
Daffodil bulbsSep 7–Oct 19
StrawberriesApr 9–Apr 23
AsparagusApr 9–Apr 23Frost probabilities
| Threshold | Spring, 90% chance later | Spring, 50% | Spring, 10% | Fall, 10% chance earlier | Fall, 50% | Fall, 90% |
|---|---|---|---|---|---|---|
| Light frost, 32°F | Apr 24 | May 7 | May 22 | Sep 23 | Oct 5 | Oct 16 |
| Hard freeze, 28°F | Apr 11 | Apr 28 | May 12 | Sep 30 | Oct 12 | Oct 25 |
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 Longmont 2 ESE (USC00055116) sits 6.9 miles from the center of Firestone at 4,950 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 Firestone, CO?
The average last frost date in Firestone is May 7, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 22.
When is the first frost in Firestone?
The first frost in fall usually comes around October 5. One year in ten it arrives before September 23.
How long is the growing season in Firestone?
About 151 days between the average last and first frost.
When should I plant tomatoes in Firestone?
Plant tomato seedlings outside from May 14 to May 28. Start seeds indoors six to eight weeks earlier.
Nearby in Colorado
- LongmontMay 7
- ErieMay 7
- JohnstownMay 10
- LafayetteMay 2
- BroomfieldMay 2
- BrightonMay 3
- ThorntonMay 2
- LouisvilleMay 6
- NorthglennMay 2
- EvansMay 2
- BoulderMay 6
- LovelandMay 10