Last frost date in Casper, WY
Expect the last frost in Casper around May 10. Frost after May 24 happens in only one year out of ten. The first fall frost usually arrives about September 29, which leaves 138 frost-free days. An early freeze before September 14 happens one year in ten.
- Safe after (10% risk)
- May 24
- Average first frost
- Sep 29
- Frost-free season
- 138 days
- Hard freeze (28°F) ends
- May 1
Frost likely Sat night, low 31°F
National Weather Service forecast, updated Oct 22, 12:24 UTC
- ThuOct 2253°
- FriOct 2334°possible frost
- SatOct 2431°frost
- SunOct 2532°frost
- MonOct 2632°frost
- TueOct 2735°possible frost
- WedOct 2835°possible frost
Planting calendar for Casper
Windows count forward or back from the average frost dates above. Click a crop for dates across Wyoming.
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 15–Oct 20
GarlicSep 8–Oct 13
Daffodil bulbsSep 1–Oct 13
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 24 | Sep 14 | Sep 29 | Oct 12 |
| Hard freeze, 28°F | Apr 17 | May 1 | May 14 | Sep 21 | Oct 6 | Oct 23 |
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 Casper Wwtp (USC00481569) sits 2.0 miles from the center of Casper at 5,097 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 Casper, WY?
The average last frost date in Casper is May 10, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after May 24.
When is the first frost in Casper?
The first frost in fall usually comes around September 29. One year in ten it arrives before September 14.
How long is the growing season in Casper?
About 138 days between the average last and first frost.
When should I plant tomatoes in Casper?
Plant tomato seedlings outside from May 17 to May 31. Start seeds indoors six to eight weeks earlier.
Nearby in Wyoming
- GilletteMay 15
- LaramieJun 7
- SheridanMay 21
- CheyenneMay 14
- Rock SpringsMay 24