Frost dates for Yellowstone Park Mammoth, WY
At Yellowstone Park Mammoth, the median last spring frost (32°F) is Jun 3 and the median first fall frost is Sep 14, for a typical growing season of 102 days. For a 90% chance that the last frost has passed, wait until Jun 19. Nearby ZIP codes are in USDA hardiness zones 4a to 5a.
- Jun 3Last spring frost (median)50% chance of 32°F after this date
- Jun 19Safer planting date10% chance of 32°F after this date
- Sep 14First fall frost (median)50% chance of 32°F by this date
- 102 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 32°F | May 18 | Jun 3 | Jun 19 |
| 28°F | May 4 | May 16 | May 30 |
| 24°F | Apr 22 | May 6 | May 18 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 32°F | Aug 31 | Sep 14 | Sep 30 |
| 28°F | Sep 13 | Sep 29 | Oct 14 |
| 24°F | Sep 26 | Oct 9 | Oct 25 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 44 days | 70 days | 93 days |
| 32°F | 77 days | 102 days | 124 days |
| 28°F | 112 days | 133 days | 153 days |
| 24°F | 135 days | 156 days | 176 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
Closest ZIP codes (each is closer to another station)
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 59030 | 4b | -25 to -20°F | 15 km |
| 59065 | 5a | -20 to -15°F | 33 km |
| 59027 | 5a | -20 to -15°F | 35 km |
| 59730 | 5a | -20 to -15°F | 43 km |
| 59758 | 4b | -25 to -20°F | 44 km |
| 59020 | 4b | -25 to -20°F | 49 km |
| 82190 | 4b | -25 to -20°F | 51 km |
| 59081 | 4a | -30 to -25°F | 56 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00489905, at 44.9767, -110.6964, elevation 1888 m (6,195 ft).
- Data quality: Standard (24+ years of data), 27 years of freeze data.
- Average days per year at or below 32°F: 202.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Tower Falls (23 km)
- Lamar Ranger Station (37 km)
- Lake Yellowstone (52 km)
- Yellowstone Lake (53 km)
- Old Faithful (59 km)
- Yellowstone National Park E Ent (77 km)
- Pahaska (78 km)
- Snake River (93 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.