Last frost date in Johnstown, CO
In Johnstown, the last spring frost comes around May 10 in an average year. Wait until May 22 if you want 90% odds of no more frost. The first fall frost usually arrives about October 1, which leaves 142 frost-free days. An early freeze before September 15 happens one year in ten.
- Safe after (10% risk)
- May 22
- Average first frost
- Oct 1
- Frost-free season
- 142 days
- Hard freeze (28°F) ends
- May 2
Frost possible in low spots Sun night, low 36°F
National Weather Service forecast, updated Oct 22, 12:57 UTC
- ThuOct 2251°
- FriOct 2346°
- SatOct 2437°
- SunOct 2536°possible frost
- MonOct 2633°possible frost
- TueOct 2734°possible frost
- WedOct 2835°possible frost
Planting calendar for Johnstown
Windows count forward or back from the average frost dates above. Click a crop for dates across Colorado.
TomatoesMay 17–May 31
PumpkinsMay 24–Jun 7
SunflowersMay 10–May 31
CucumbersMay 24–May 31
CornMay 17–May 31
Sweet potatoesMay 31–Jun 14
WatermelonMay 24–Jun 7
Green beansMay 17–Jun 7
ZucchiniMay 17–May 31
OkraMay 31–Jun 14
PeppersMay 24–Jun 7
BasilMay 17–May 31
Butternut squashMay 17–May 31
CantaloupeMay 24–Jun 7
EggplantMay 24–Jun 7
PotatoesApr 12–Apr 26
OnionsMar 29–Apr 19
CarrotsApr 19–May 24
LettuceApr 26–May 17
BroccoliApr 12–Apr 26
BeetsApr 12–May 24
PeasMar 29–Apr 12
CabbageApr 12–Apr 26
RadishesApr 5–May 17
Brussels sproutsApr 26–May 10
SpinachMar 29–Apr 19
CilantroApr 26–May 17
KaleApr 12–Apr 26
Collard greensApr 12–Apr 26
TurnipsApr 12–Apr 26
DillMay 10–May 24
CeleryMay 17–May 24
CauliflowerApr 26–May 10
LeeksApr 26–May 10
Swiss chardApr 26–May 24
ParsleyApr 26–May 17
Tulip bulbsSep 17–Oct 22
GarlicSep 10–Oct 15
Daffodil bulbsSep 3–Oct 15
StrawberriesApr 12–Apr 26
AsparagusApr 12–Apr 26Frost probabilities
| Threshold | Spring, 90% chance later | Spring, 50% | Spring, 10% | Fall, 10% chance earlier | Fall, 50% | Fall, 90% |
|---|---|---|---|---|---|---|
| Light frost, 32°F | Apr 30 | May 10 | May 22 | Sep 15 | Oct 1 | Oct 13 |
| Hard freeze, 28°F | Apr 17 | May 2 | May 14 | Sep 22 | Oct 10 | Oct 22 |
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 Loveland 2N (USC00055236) sits 12.7 miles from the center of Johnstown at 5,080 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 Johnstown, CO?
The average last frost date in Johnstown is May 10, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 22.
When is the first frost in Johnstown?
The first frost in fall usually comes around October 1. One year in ten it arrives before September 15.
How long is the growing season in Johnstown?
About 142 days between the average last and first frost.
When should I plant tomatoes in Johnstown?
Plant tomato seedlings outside from May 17 to May 31. Start seeds indoors six to eight weeks earlier.
Nearby in Colorado
- EvansMay 2
- GreeleyMay 2
- FirestoneMay 7
- LovelandMay 10
- WindsorMay 3
- LongmontMay 7
- Fort CollinsMay 2
- ErieMay 7
- LafayetteMay 2
- BrightonMay 3
- BroomfieldMay 2
- LouisvilleMay 6