Last frost date in Northglenn, CO
The average last frost in Northglenn is May 2. By May 14 the chance of another 32°F night drops to 1 in 10. The first fall frost usually arrives about October 11, which leaves 160 frost-free days. An early freeze before September 26 happens one year in ten.
- Safe after (10% risk)
- May 14
- Average first frost
- Oct 11
- Frost-free season
- 160 days
- Hard freeze (28°F) ends
- Apr 20
No frost in the next 7 nights
Later than usual: the average first frost here is October 11.
National Weather Service forecast, updated Oct 22, 12:57 UTC
- ThuOct 2257°
- FriOct 2349°
- SatOct 2441°
- SunOct 2540°
- MonOct 2638°
- TueOct 2739°
- WedOct 2841°
Planting calendar for Northglenn
Windows count forward or back from the average frost dates above. Click a crop for dates across Colorado.
TomatoesMay 9–May 23
PumpkinsMay 16–May 30
SunflowersMay 2–May 23
CucumbersMay 16–May 23
CornMay 9–May 23
Sweet potatoesMay 23–Jun 6
WatermelonMay 16–May 30
Green beansMay 9–May 30
ZucchiniMay 9–May 23
OkraMay 23–Jun 6
PeppersMay 16–May 30
BasilMay 9–May 23
Butternut squashMay 9–May 23
CantaloupeMay 16–May 30
EggplantMay 16–May 30
PotatoesApr 4–Apr 18
OnionsMar 21–Apr 11
CarrotsApr 11–May 16
LettuceApr 18–May 9
BroccoliApr 4–Apr 18
BeetsApr 4–May 16
PeasMar 21–Apr 4
CabbageApr 4–Apr 18
RadishesMar 28–May 9
Brussels sproutsApr 18–May 2
SpinachMar 21–Apr 11
CilantroApr 18–May 9
KaleApr 4–Apr 18
Collard greensApr 4–Apr 18
TurnipsApr 4–Apr 18
DillMay 2–May 16
CeleryMay 9–May 16
CauliflowerApr 18–May 2
LeeksApr 18–May 2
Swiss chardApr 18–May 16
ParsleyApr 18–May 9
Tulip bulbsSep 27–Nov 1
GarlicSep 20–Oct 25
Daffodil bulbsSep 13–Oct 25
StrawberriesApr 4–Apr 18
AsparagusApr 4–Apr 18Frost probabilities
| Threshold | Spring, 90% chance later | Spring, 50% | Spring, 10% | Fall, 10% chance earlier | Fall, 50% | Fall, 90% |
|---|---|---|---|---|---|---|
| Light frost, 32°F | Apr 18 | May 2 | May 14 | Sep 26 | Oct 11 | Oct 24 |
| Hard freeze, 28°F | Apr 4 | Apr 20 | May 5 | Oct 7 | Oct 21 | Nov 4 |
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 Northglenn (USC00055984) sits 1.9 miles from the center of Northglenn at 5,407 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 Northglenn, CO?
The average last frost date in Northglenn is May 2, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 14.
When is the first frost in Northglenn?
The first frost in fall usually comes around October 11. One year in ten it arrives before September 26.
How long is the growing season in Northglenn?
About 160 days between the average last and first frost.
When should I plant tomatoes in Northglenn?
Plant tomato seedlings outside from May 9 to May 23. Start seeds indoors six to eight weeks earlier.
Nearby in Colorado
- ThorntonMay 2
- BroomfieldMay 2
- WestminsterMay 2
- LafayetteMay 2
- ErieMay 7
- LouisvilleMay 6
- Commerce CityMay 3
- ArvadaMay 5
- BrightonMay 3
- Wheat RidgeMay 5
- DenverMay 4
- BoulderMay 6