Frost dates for Prosser, WA
At Prosser, the median last spring frost (32°F) is Apr 14 and the median first fall frost is Oct 22, for a typical growing season of 189 days. For a 90% chance that the last frost has passed, wait until May 7. Nearby ZIP codes are in USDA hardiness zone 7b.
- Apr 14Last spring frost (median)50% chance of 32°F after this date
- May 7Safer planting date10% chance of 32°F after this date
- Oct 22First fall frost (median)50% chance of 32°F by this date
- 189 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 | Apr 16 | May 2 | May 24 |
| 32°F | Mar 24 | Apr 14 | May 7 |
| 28°F | Mar 2 | Mar 23 | Apr 22 |
| 24°F | Feb 13 | Mar 3 | Mar 31 |
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 26 | Oct 9 | Oct 25 |
| 32°F | Oct 5 | Oct 22 | Nov 7 |
| 28°F | Oct 18 | Nov 2 | Nov 20 |
| 24°F | Oct 27 | Nov 13 | Dec 1 |
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 | 130 days | 158 days | 183 days |
| 32°F | 161 days | 189 days | 217 days |
| 28°F | 191 days | 224 days | 249 days |
| 24°F | 223 days | 254 days | 279 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 |
|---|---|---|---|
| 99350 | 7b | 5 to 10°F | 7 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 USC00456768, at 46.2014, -119.7581, elevation 253 m (830 ft).
- Data quality: Representative (10+ years), 25 years of freeze data.
- Average days per year at or below 32°F: 109.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Sunnyside (24 km)
- Sunnyside #2 (26 km)
- Richland (40 km)
- McNary Dam (46 km)
- Moxee City 10 E (46 km)
- Bickleton (48 km)
- Pasco Tri Cities Airport (50 km)
- Kennewick (51 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.