Frost Dates: First and last frost dates for Cottage Grove Dam, OR
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 29, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
- Around May 12, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
- Before May 1, 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° | Jan 28 | Jan 10 | Dec 20 | -- | -- | -- | -- | -- | -- |
| Last 20° | Feb 13 | Feb 4 | Jan 29 | Jan 23 | Jan 17 | Jan 10 | Dec 31 | -- | -- |
| Last 24° | Feb 27 | Feb 18 | Feb 11 | Feb 5 | Jan 31 | Jan 24 | Jan 16 | Jan 2 | -- |
| Last 28° | Mar 30 | Mar 19 | Mar 12 | Mar 5 | Feb 27 | Feb 21 | Feb 14 | Feb 6 | Jan 27 |
| Last 32° | May 6 | Apr 27 | Apr 22 | Apr 17 | Apr 12 | Apr 7 | Apr 2 | Mar 27 | Mar 19 |
| Last 36° | May 29 | May 23 | May 19 | May 16 | May 12 | May 9 | May 5 | May 1 | Apr 25 |
ℹ️ How to read these charts for the fall
As summer ends in Cottage Grove Dam, OR, 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° | Dec 14 | Jan 4 | Jan 28 | -- | -- | -- | -- | -- | -- |
| First 20° | Dec 8 | Dec 22 | Jan 2 | Jan 12 | Jan 22 | Feb 3 | Feb 26 | -- | -- |
| First 24° | Nov 21 | Dec 2 | Dec 9 | Dec 16 | Dec 23 | Dec 30 | Jan 8 | Jan 24 | -- |
| First 28° | Oct 25 | Nov 3 | Nov 10 | Nov 16 | Nov 22 | Nov 28 | Dec 4 | Dec 11 | Dec 20 |
| First 32° | Oct 13 | Oct 20 | Oct 24 | Oct 29 | Nov 1 | Nov 5 | Nov 9 | Nov 14 | Nov 21 |
| First 36° | Sep 21 | Sep 27 | Oct 2 | Oct 6 | Oct 10 | Oct 14 | Oct 18 | Oct 22 | Oct 29 |
📍 Frost Dates for other nearby locations
- Cottage Grove, OR 5.6 mi
- Dorena, OR 7.9 mi
- Drain, OR 19.2 mi
- Idleyld Park, OR 24.6 mi
- Lookout Point Dam, OR 24.6 mi
- Eugene-mahlon Sweet Fld, OR 30.8 mi
- Fern Ridge-veneta, OR 31.8 mi
- Leaburg, OR 36.8 mi
- Elkton, OR 38.5 mi
- Roseburg Kqen, OR 40.9 mi
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Data is provided by the NOAA National Centers for Environmental Information.