Last spring frost
Apr 8
Frost Dates for Rock Island, WA
First fall frost
Oct 24
Growing season
200 days
Hardiness zone
7a
In an average year around Rock Island, WA, the last spring frost (32°F) is about Apr 8 and the first fall frost is about Oct 24, giving roughly a 200-day growing season. To be safe most years, wait until Mar 20 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 8 | Apr 25 | Apr 11 |
| Freeze (32°F) | Apr 23 | Apr 8 | Mar 20 |
| Hard (28°F) | Apr 6 | Mar 17 | Mar 2 |
| Severe (24°F) | Mar 19 | Mar 2 | Feb 11 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 8 | May 3 | Apr 30 | Apr 27 | Apr 25 | Apr 23 | Apr 20 | Apr 16 | Apr 11 |
| 32°F | Apr 23 | Apr 17 | Apr 14 | Apr 10 | Apr 8 | Apr 4 | Apr 1 | Mar 28 | Mar 20 |
| 28°F | Apr 6 | Apr 1 | Mar 27 | Mar 22 | Mar 17 | Mar 13 | Mar 9 | Mar 6 | Mar 2 |
| 24°F | Mar 19 | Mar 13 | Mar 8 | Mar 5 | Mar 2 | Feb 28 | Feb 23 | Feb 18 | Feb 11 |
| 20°F | Mar 8 | Mar 1 | Feb 26 | Feb 21 | Feb 17 | Feb 13 | Feb 7 | Feb 2 | Jan 25 |
| 16°F | Feb 26 | Feb 20 | Feb 13 | Feb 8 | Feb 3 | Jan 29 | Jan 22 | Jan 15 | 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) | Oct 3 | Oct 14 | Oct 25 |
| Freeze (32°F) | Oct 12 | Oct 24 | Nov 5 |
| Hard (28°F) | Oct 20 | Nov 4 | Nov 18 |
| Severe (24°F) | Oct 29 | Nov 15 | Dec 4 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 3 | Oct 7 | Oct 10 | Oct 12 | Oct 14 | Oct 16 | Oct 19 | Oct 21 | Oct 25 |
| 32°F | Oct 12 | Oct 16 | Oct 19 | Oct 22 | Oct 24 | Oct 26 | Oct 29 | Nov 1 | Nov 5 |
| 28°F | Oct 20 | Oct 25 | Oct 29 | Nov 1 | Nov 4 | Nov 6 | Nov 9 | Nov 13 | Nov 18 |
| 24°F | Oct 29 | Nov 3 | Nov 8 | Nov 12 | Nov 15 | Nov 18 | Nov 23 | Nov 27 | Dec 4 |
| 20°F | Nov 10 | Nov 15 | Nov 20 | Nov 24 | Nov 28 | Dec 3 | Dec 7 | Dec 13 | Dec 24 |
| 16°F | Nov 21 | Nov 28 | Dec 2 | Dec 6 | Dec 11 | Dec 17 | Dec 23 | Dec 30 | Jan 10 |
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: Wenatchee Pangborn Ap, Wa, about 7.6 miles away@if(!empty($station['elevation_ft'])), at 1,229 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 Rock Island, WA?
On average, the last spring frost (32°F) around Rock Island, WA is about Apr 8. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 20.
When is the first frost in the fall?
The first fall frost around Rock Island, WA typically arrives about Oct 24. 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 8 on average, or Mar 20 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 200 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 98850 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026