Last spring frost
May 4
Frost Dates for Zillah, WA
First fall frost
Oct 10
Growing season
155 days
Hardiness zone
7a
In an average year around Zillah, WA, the last spring frost (32°F) is about May 4 and the first fall frost is about Oct 10, giving roughly a 155-day growing season. To be safe most years, wait until Apr 21 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Jun 12 | May 23 | May 6 |
| Freeze (32°F) | May 23 | May 4 | Apr 21 |
| Hard (28°F) | May 5 | Apr 18 | Mar 29 |
| Severe (24°F) | Apr 16 | Mar 25 | Mar 2 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 12 | Jun 5 | May 31 | May 27 | May 23 | May 19 | May 15 | May 10 | May 6 |
| 32°F | May 23 | May 16 | May 11 | May 8 | May 4 | May 1 | Apr 29 | Apr 26 | Apr 21 |
| 28°F | May 5 | Apr 30 | Apr 26 | Apr 22 | Apr 18 | Apr 14 | Apr 9 | Apr 4 | Mar 29 |
| 24°F | Apr 16 | Apr 7 | Apr 2 | Mar 30 | Mar 25 | Mar 19 | Mar 14 | Mar 9 | Mar 2 |
| 20°F | Mar 27 | Mar 17 | Mar 12 | Mar 7 | Mar 2 | Feb 27 | Feb 21 | Feb 14 | Feb 3 |
| 16°F | Mar 9 | Mar 1 | Feb 24 | Feb 19 | Feb 13 | Feb 5 | Jan 27 | Jan 17 | Jan 4 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Sep 11 | Sep 27 | Oct 10 |
| Freeze (32°F) | Sep 26 | Oct 10 | Oct 25 |
| Hard (28°F) | Oct 5 | Oct 23 | Nov 6 |
| Severe (24°F) | Oct 20 | Nov 4 | Nov 20 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 11 | Sep 17 | Sep 21 | Sep 24 | Sep 27 | Sep 30 | Oct 2 | Oct 5 | Oct 10 |
| 32°F | Sep 26 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 20 | Oct 25 |
| 28°F | Oct 5 | Oct 12 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 6 |
| 24°F | Oct 20 | Oct 25 | Oct 29 | Nov 1 | Nov 4 | Nov 7 | Nov 10 | Nov 14 | Nov 20 |
| 20°F | Oct 29 | Nov 3 | Nov 8 | Nov 11 | Nov 15 | Nov 20 | Nov 24 | Nov 28 | Dec 5 |
| 16°F | Nov 8 | Nov 14 | Nov 20 | Nov 25 | Nov 29 | Dec 4 | Dec 11 | Dec 21 | Jan 1 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Moxee City 10 E, Wa, about 1.9 miles away@if(!empty($station['elevation_ft'])), at 1,550 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Zillah, WA?
On average, the last spring frost (32°F) around Zillah, WA is about May 4. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 21.
When is the first frost in the fall?
The first fall frost around Zillah, WA typically arrives about Oct 10. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around May 4 on average, or Apr 21 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 155 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 98936 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026