Frost dates for Whitman Mission, WA
At Whitman Mission, the median last spring frost (32°F) is May 2 and the median first fall frost is Oct 1, for a typical growing season of 151 days. For a 90% chance that the last frost has passed, wait until May 18. Nearby ZIP codes are in USDA hardiness zone 7a.
- May 2Last spring frost (median)50% chance of 32°F after this date
- May 18Safer planting date10% chance of 32°F after this date
- Oct 1First fall frost (median)50% chance of 32°F by this date
- 151 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 3 | May 18 | Jun 7 |
| 32°F | Apr 16 | May 2 | May 18 |
| 28°F | Mar 23 | Apr 15 | May 1 |
| 24°F | Feb 28 | Mar 20 | Apr 16 |
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 | Sep 1 | Sep 17 | Oct 2 |
| 32°F | Sep 14 | Oct 1 | Oct 16 |
| 28°F | Sep 28 | Oct 12 | Oct 30 |
| 24°F | Oct 7 | Oct 27 | Nov 23 |
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 | 93 days | 121 days | 143 days |
| 32°F | 128 days | 151 days | 172 days |
| 28°F | 156 days | 181 days | 208 days |
| 24°F | 189 days | 220 days | 252 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 |
|---|---|---|---|
| 99324 | 7a | 0 to 5°F | 6 km |
| 99360 | 7a | 0 to 5°F | 17 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 USC00459200, at 46.0436, -118.4628, elevation 193 m (632 ft).
- Data quality: Standard (24+ years of data), 29 years of freeze data.
- Average days per year at or below 32°F: 125.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Walla Walla Regional Airport (15 km)
- Ice Harbor Dam (39 km)
- Dayton 1 WSW (47 km)
- Kennewick (53 km)
- Pasco Tri Cities Airport (56 km)
- Sagemoor (61 km)
- McNary Dam (66 km)
- Eltopia 8 WSW (66 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.