Last spring frost
Apr 7
Frost Dates for Onalaska, WA
First fall frost
Nov 13
Growing season
215 days
Hardiness zone
8b
In an average year around Onalaska, WA, the last spring frost (32°F) is about Apr 7 and the first fall frost is about Nov 13, giving roughly a 215-day growing season. To be safe most years, wait until Mar 16 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) | May 23 | May 6 | Apr 17 |
| Freeze (32°F) | May 8 | Apr 7 | Mar 16 |
| Hard (28°F) | Apr 2 | Mar 6 | Jan 31 |
| Severe (24°F) | Mar 1 | Jan 31 | Dec 12 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 23 | May 17 | May 14 | May 10 | May 6 | May 2 | Apr 28 | Apr 24 | Apr 17 |
| 32°F | May 8 | Apr 30 | Apr 24 | Apr 15 | Apr 7 | Apr 2 | Mar 29 | Mar 24 | Mar 16 |
| 28°F | Apr 2 | Mar 24 | Mar 19 | Mar 13 | Mar 6 | Feb 28 | Feb 24 | Feb 16 | Jan 31 |
| 24°F | Mar 1 | Feb 24 | Feb 16 | Feb 8 | Jan 31 | Jan 18 | Jan 7 | Dec 31 | Dec 12 |
| 20°F | Feb 17 | Feb 8 | Jan 30 | Jan 19 | Jan 4 | Dec 30 | Dec 21 | Dec 13 | Dec 5 |
| 16°F | Feb 9 | Feb 2 | Jan 16 | Jan 3 | Dec 31 | Dec 22 | Dec 15 | Dec 9 | Dec 3 |
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) | Oct 4 | Oct 24 | Nov 11 |
| Freeze (32°F) | Oct 24 | Nov 13 | Dec 4 |
| Hard (28°F) | Nov 8 | Dec 1 | Jan 1 |
| Severe (24°F) | Nov 23 | Dec 19 | Feb 7 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 4 | Oct 12 | Oct 17 | Oct 20 | Oct 24 | Oct 27 | Oct 30 | Nov 4 | Nov 11 |
| 32°F | Oct 24 | Oct 30 | Nov 5 | Nov 9 | Nov 13 | Nov 17 | Nov 22 | Nov 27 | Dec 4 |
| 28°F | Nov 8 | Nov 16 | Nov 23 | Nov 27 | Dec 1 | Dec 5 | Dec 13 | Dec 20 | Jan 1 |
| 24°F | Nov 23 | Nov 30 | Dec 5 | Dec 11 | Dec 19 | Dec 25 | Jan 2 | Jan 20 | Feb 7 |
| 20°F | Nov 30 | Dec 5 | Dec 10 | Dec 17 | Dec 25 | Jan 1 | Jan 13 | Jan 29 | Feb 11 |
| 16°F | Dec 2 | Dec 7 | Dec 11 | Dec 18 | Dec 24 | Jan 1 | Jan 12 | Jan 30 | Feb 6 |
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: Mayfield Pwr Plt, Wa, about 2 miles away@if(!empty($station['elevation_ft'])), at 280 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 Onalaska, WA?
On average, the last spring frost (32°F) around Onalaska, WA is about Apr 7. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 16.
When is the first frost in the fall?
The first fall frost around Onalaska, WA typically arrives about Nov 13. 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 Apr 7 on average, or Mar 16 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 215 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 98582 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026