Frost dates for Smyrna, WA
At Smyrna, the median last spring frost (32°F) is Apr 23 and the median first fall frost is Oct 12, for a typical growing season of 172 days. For a 90% chance that the last frost has passed, wait until May 7. Nearby ZIP codes are in USDA hardiness zones 7a to 7b.
- Apr 23Last spring frost (median)50% chance of 32°F after this date
- May 7Safer planting date10% chance of 32°F after this date
- Oct 12First fall frost (median)50% chance of 32°F by this date
- 172 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 23 | May 6 | May 18 |
| 32°F | Apr 3 | Apr 23 | May 7 |
| 28°F | Mar 13 | Apr 3 | Apr 24 |
| 24°F | Feb 24 | Mar 15 | Apr 5 |
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 21 | Oct 2 | Oct 14 |
| 32°F | Oct 1 | Oct 12 | Oct 25 |
| 28°F | Oct 6 | Oct 24 | Nov 6 |
| 24°F | Oct 20 | Nov 2 | Nov 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 | 131 days | 148 days | 167 days |
| 32°F | 152 days | 172 days | 192 days |
| 28°F | 176 days | 202 days | 227 days |
| 24°F | 205 days | 231 days | 261 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 |
|---|---|---|---|
| 99357 | 7a | 0 to 5°F | 6 km |
| 99349 | 7a | 0 to 5°F | 12 km |
| 99321 | 7b | 5 to 10°F | 18 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 USC00457727, at 46.8367, -119.6633, elevation 171 m (560 ft).
- Data quality: Representative (10+ years), 15 years of freeze data.
- Average days per year at or below 32°F: 122.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Priest Rapids Dam (28 km)
- Quincy (45 km)
- Moses Lake Grant Co Airport (49 km)
- Moxee City 10 E (53 km)
- Ephrata Muni Airport (54 km)
- Sunnyside #2 (61 km)
- Eltopia 8 WSW (62 km)
- Connell 1 W (62 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.