Last frost date in Rock Springs, WY
In Rock Springs, the last spring frost comes around May 24 in an average year. Wait until June 9 if you want 90% odds of no more frost. The first fall frost usually arrives about September 24, which leaves 121 frost-free days. An early freeze before September 9 happens one year in ten.
- Safe after (10% risk)
- Jun 9
- Average first frost
- Sep 24
- Frost-free season
- 121 days
- Hard freeze (28°F) ends
- May 9
Frost likely Sat night, low 30°F
National Weather Service forecast, updated Oct 22, 12:57 UTC
- ThuOct 2242°
- FriOct 2333°possible frost
- SatOct 2430°frost
- SunOct 2529°frost
- MonOct 2630°frost
- TueOct 2730°frost
- WedOct 2831°frost
Planting calendar for Rock Springs
Windows count forward or back from the average frost dates above. Click a crop for dates across Wyoming.
TomatoesMay 31–Jun 14
PumpkinsJun 7–Jun 21
SunflowersMay 24–Jun 14
CucumbersJun 7–Jun 14
CornMay 31–Jun 14
Sweet potatoesJun 14–Jun 28
WatermelonJun 7–Jun 21
Green beansMay 31–Jun 21
ZucchiniMay 31–Jun 14
OkraJun 14–Jun 28
PeppersJun 7–Jun 21
BasilMay 31–Jun 14
Butternut squashMay 31–Jun 14
CantaloupeJun 7–Jun 21
EggplantJun 7–Jun 21
PotatoesApr 26–May 10
OnionsApr 12–May 3
CarrotsMay 3–Jun 7
LettuceMay 10–May 31
BroccoliApr 26–May 10
BeetsApr 26–Jun 7
PeasApr 12–Apr 26
CabbageApr 26–May 10
RadishesApr 19–May 31
Brussels sproutsMay 10–May 24
SpinachApr 12–May 3
CilantroMay 10–May 31
KaleApr 26–May 10
Collard greensApr 26–May 10
TurnipsApr 26–May 10
DillMay 24–Jun 7
CeleryMay 31–Jun 7
CauliflowerMay 10–May 24
LeeksMay 10–May 24
Swiss chardMay 10–Jun 7
ParsleyMay 10–May 31
Tulip bulbsSep 10–Oct 15
GarlicSep 3–Oct 8
Daffodil bulbsAug 27–Oct 8
StrawberriesApr 26–May 10
AsparagusApr 26–May 10The frost-free season here is short for pumpkins, sweet potatoes, butternut squash. Start them indoors and look for early varieties.
Frost probabilities
| Threshold | Spring, 90% chance later | Spring, 50% | Spring, 10% | Fall, 10% chance earlier | Fall, 50% | Fall, 90% |
|---|---|---|---|---|---|---|
| Light frost, 32°F | May 8 | May 24 | Jun 9 | Sep 9 | Sep 24 | Oct 4 |
| Hard freeze, 28°F | Apr 25 | May 9 | May 26 | Sep 19 | Oct 3 | Oct 17 |
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 Rock Springs Fire Dept (USC00487847) sits 1.5 miles from the center of Rock Springs at 6,270 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 Rock Springs, WY?
The average last frost date in Rock Springs is May 24, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after June 9.
When is the first frost in Rock Springs?
The first frost in fall usually comes around September 24. One year in ten it arrives before September 9.
How long is the growing season in Rock Springs?
About 121 days between the average last and first frost.
When should I plant tomatoes in Rock Springs?
Plant tomato seedlings outside from May 31 to June 14. Start seeds indoors six to eight weeks earlier.