Frost Dates: First and last frost dates for Diablo Dam, WA
ℹ️ How to read these charts for the spring
As spring unfolds, the risk of frost gradually decreases each day until your tender plants are finally safe. The probabilities shown in the chart help you make smart decisions about when to plant.
While frost typically forms at 32°F, tender plants can be damaged even when temperatures are slightly higher. Air temperatures are often measured several feet above the ground, but temperatures at plant level can be several degrees colder. Protected areas like porches help by blocking radiational cooling. Given these variables, we consider 36°F the "caution zone" for frost-sensitive plants.
Key dates for your spring planting:
- By May 26, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
- Around May 8, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
- Before April 26, there's still an 80% risk of frost — too early for tomatoes and other tender plants unless you're prepared to protect them
If the 10-day forecast shows no temperatures below 40°F, you might safely plant earlier than the above dates suggest. Many gardeners watch for this weather window to get a head start on the growing season.
| Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| Last 16° | Feb 24 | Feb 14 | Feb 6 | Jan 30 | Jan 23 | Jan 16 | Jan 7 | Dec 21 | -- |
| Last 20° | Mar 3 | Feb 22 | Feb 15 | Feb 9 | Feb 3 | Jan 28 | Jan 22 | Jan 12 | -- |
| Last 24° | Mar 9 | Feb 28 | Feb 22 | Feb 17 | Feb 12 | Feb 7 | Feb 1 | Jan 26 | Jan 17 |
| Last 28° | Apr 4 | Mar 25 | Mar 18 | Mar 12 | Mar 7 | Mar 1 | Feb 23 | Feb 16 | Feb 7 |
| Last 32° | May 6 | Apr 30 | Apr 26 | Apr 22 | Apr 19 | Apr 15 | Apr 12 | Apr 8 | Apr 2 |
| Last 36° | May 26 | May 20 | May 15 | May 11 | May 8 | May 4 | Apr 30 | Apr 26 | Apr 20 |
ℹ️ How to read these charts for the fall
As summer ends in Diablo Dam, WA, nighttime temperatures begin to drop, and your risk of frost increases with each passing day. Knowing when to expect frost helps you harvest sensitive crops and extend your growing season with protection methods.
The chart below shows the probability of experiencing specific temperatures on various dates. Here's what this means for your garden:
These probabilities help you time your end-of-season harvests and know when to apply protective measures like row covers, cloches, or cold frames to extend your harvest.
| Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| First 16° | Nov 28 | Dec 10 | Dec 20 | Dec 28 | Jan 5 | Jan 15 | Jan 27 | -- | -- |
| First 20° | Nov 18 | Nov 28 | Dec 6 | Dec 13 | Dec 19 | Dec 26 | Jan 3 | Jan 13 | -- |
| First 24° | Nov 12 | Nov 22 | Nov 29 | Dec 5 | Dec 11 | Dec 17 | Dec 23 | Dec 30 | Jan 9 |
| First 28° | Oct 28 | Nov 5 | Nov 11 | Nov 16 | Nov 21 | Nov 26 | Dec 1 | Dec 7 | Dec 16 |
| First 32° | Oct 14 | Oct 19 | Oct 23 | Oct 27 | Oct 30 | Nov 2 | Nov 5 | Nov 9 | Nov 15 |
| First 36° | Sep 29 | Oct 4 | Oct 8 | Oct 11 | Oct 14 | Oct 17 | Oct 20 | Oct 24 | Oct 29 |
📍 Frost Dates for other nearby locations
- Ross Dam, WA 4.2 mi
- Newhalem, WA 8.1 mi
- Stehekin, WA 37.6 mi
- Upper Baker Dam, WA 39.1 mi
- Holden Village, WA 43.4 mi
- Concrete Ppl Fish Stn, WA 44.0 mi
- Darrington Rs, WA 45.4 mi
- Mazama, WA 50.9 mi
- Chilliwack, BC 64.5 mi
- Winthrop, WA 67.3 mi
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Data is provided by the NOAA National Centers for Environmental Information.