Last spring frost
Apr 18
Frost Dates for Carbonado, WA
First fall frost
Oct 31
Growing season
196 days
Hardiness zone
8b
In an average year around Carbonado, WA, the last spring frost (32°F) is about Apr 18 and the first fall frost is about Oct 31, giving roughly a 196-day growing season. To be safe most years, wait until Mar 28 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 26 | May 6 | Apr 21 |
| Freeze (32°F) | May 10 | Apr 18 | Mar 28 |
| Hard (28°F) | Apr 11 | Mar 15 | Feb 13 |
| Severe (24°F) | Mar 3 | Feb 11 | Dec 29 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 26 | May 19 | May 14 | May 10 | May 6 | May 2 | Apr 30 | Apr 26 | Apr 21 |
| 32°F | May 10 | May 2 | Apr 28 | Apr 23 | Apr 18 | Apr 13 | Apr 8 | Apr 2 | Mar 28 |
| 28°F | Apr 11 | Apr 2 | Mar 27 | Mar 22 | Mar 15 | Mar 9 | Mar 2 | Feb 25 | Feb 13 |
| 24°F | Mar 3 | Feb 27 | Feb 22 | Feb 18 | Feb 11 | Feb 4 | Jan 28 | Jan 15 | Dec 29 |
| 20°F | Feb 20 | Feb 13 | Feb 4 | Jan 30 | Jan 18 | Jan 5 | Dec 23 | Dec 12 | Dec 3 |
| 16°F | Feb 14 | Feb 3 | Jan 29 | Jan 12 | Dec 30 | Dec 19 | Dec 13 | Dec 8 | Dec 1 |
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 26 | Oct 12 | Nov 1 |
| Freeze (32°F) | Oct 8 | Oct 31 | Nov 21 |
| Hard (28°F) | Oct 30 | Nov 17 | Dec 11 |
| Severe (24°F) | Nov 11 | Dec 3 | Jan 18 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 26 | Oct 2 | Oct 5 | Oct 8 | Oct 12 | Oct 17 | Oct 21 | Oct 25 | Nov 1 |
| 32°F | Oct 8 | Oct 18 | Oct 23 | Oct 28 | Oct 31 | Nov 3 | Nov 7 | Nov 14 | Nov 21 |
| 28°F | Oct 30 | Nov 4 | Nov 9 | Nov 13 | Nov 17 | Nov 22 | Nov 26 | Dec 3 | Dec 11 |
| 24°F | Nov 11 | Nov 19 | Nov 24 | Nov 29 | Dec 3 | Dec 10 | Dec 17 | Dec 31 | Jan 18 |
| 20°F | Nov 23 | Nov 29 | Dec 3 | Dec 8 | Dec 16 | Dec 28 | Jan 5 | Jan 22 | Feb 5 |
| 16°F | Nov 26 | Dec 2 | Dec 7 | Dec 12 | Dec 17 | Dec 29 | Jan 16 | Jan 30 | Feb 11 |
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: Mud Mtn Dam, Wa, about 11.4 miles away@if(!empty($station['elevation_ft'])), at 1,308 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 Carbonado, WA?
On average, the last spring frost (32°F) around Carbonado, WA is about Apr 18. In cooler years it can run later, so for a safer bet many gardeners wait until Mar 28.
When is the first frost in the fall?
The first fall frost around Carbonado, WA typically arrives about Oct 31. 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 18 on average, or Mar 28 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 196 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 98323 Planting calendar → Washington frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026