Frost dates for Rosalia, WA
At Rosalia, the median last spring frost (32°F) is May 7 and the median first fall frost is Sep 28, for a typical growing season of 144 days. For a 90% chance that the last frost has passed, wait until May 25. Nearby ZIP codes are in USDA hardiness zone 6b.
- May 7Last spring frost (median)50% chance of 32°F after this date
- May 25Safer planting date10% chance of 32°F after this date
- Sep 28First fall frost (median)50% chance of 32°F by this date
- 144 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 |
|---|---|---|---|
| 36°F | May 8 | May 31 | Jul 5 |
| 32°F | Apr 22 | May 7 | May 25 |
| 28°F | Mar 25 | Apr 20 | May 8 |
| 24°F | Feb 28 | Mar 22 | Apr 20 |
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 |
|---|---|---|---|
| 36°F | Aug 26 | Sep 13 | Sep 28 |
| 32°F | Sep 11 | Sep 28 | Oct 16 |
| 28°F | Sep 25 | Oct 12 | Nov 2 |
| 24°F | Oct 6 | Oct 28 | Nov 20 |
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 | 68 days | 103 days | 132 days |
| 32°F | 117 days | 144 days | 167 days |
| 28°F | 149 days | 175 days | 206 days |
| 24°F | 181 days | 216 days | 249 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 99170 | 6b | -5 to 0°F | 3 km |
| 99149 | 6b | -5 to 0°F | 8 km |
| 99158 | 6b | -5 to 0°F | 15 km |
| 99039 | 6b | -5 to 0°F | 15 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 USC00457180, at 47.2347, -117.3636, elevation 738 m (2,420 ft).
- Data quality: Representative (10+ years), 22 years of freeze data.
- Average days per year at or below 32°F: 146.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- St. John (23 km)
- Spokane 17 SSW (24 km)
- Spokane Intl Airport (45 km)
- Spokane Felts Field (50 km)
- Spokane WFO (53 km)
- Pullman 2 NW (54 km)
- Pullman Moscow Regional Airport (58 km)
- Lacrosse (61 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.