Frost Dates: First and last frost dates for Tidewater, OR
What's a safe temperature for tender plants? When the nightly temperature falls, frost can form, even above 32°, because the air is colder high above the ground and the frost can form up there and then fall down onto your garden and do some damage, even if it's 36° on the ground. So many factors come into play, including wind, concrete, houses, trees and other structures, etc etc etc. Because of all this, you might want to consider 36° as "the danger zone".
In your average springtime, you have a 90% chance that there will be no 36° nights by May 23. In other words, you can pretty much count on being safe from frost by that day. But we want to get those tomatoes in the ground as soon as possible, right? We see that there's still an 80% chance of 36° on April 17, so we don't dare plant that early. We wait a few days and by May 1 we are at the 50/50 point. At this point, we are close and we can start watching the weather forecast. If the upcoming week's forecast doesn't show below 40°, then it's probably okay to risk planting out your plants.
| Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| Last 16° | Jan 11 | Dec 23 | -- | -- | -- | -- | -- | -- | -- |
| Last 20° | Jan 26 | Jan 8 | Dec 23 | Nov 28 | -- | -- | -- | -- | -- |
| Last 24° | Feb 9 | Jan 29 | Jan 21 | Jan 13 | Jan 5 | Dec 26 | -- | -- | -- |
| Last 28° | Mar 6 | Feb 23 | Feb 14 | Feb 8 | Feb 1 | Jan 25 | Jan 18 | Jan 8 | Dec 21 |
| Last 32° | May 3 | Apr 23 | Apr 15 | Apr 8 | Apr 2 | Mar 27 | Mar 21 | Mar 13 | Mar 2 |
| Last 36° | May 23 | May 15 | May 10 | May 6 | May 1 | Apr 27 | Apr 23 | Apr 17 | Apr 10 |
The charts on this page show the probabilities of receiving a certain temperature on a certain day. Some examples that might help:
- You have a small 20% chance of getting 32° by October 27.
- There is a 50% chance of being hit by a 32° frost starting around November 13
- You have a 80% chance of seeing 32° by November 30
- Said another way, you have a 1 in 5 chance at making it to that day without a 32° night.
| Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| First 16° | Dec 26 | Jan 15 | -- | -- | -- | -- | -- | -- | -- |
| First 20° | Dec 8 | Dec 24 | Jan 8 | Feb 1 | -- | -- | -- | -- | -- |
| First 24° | Nov 29 | Dec 12 | Dec 23 | Jan 2 | Jan 13 | Jan 29 | -- | -- | -- |
| First 28° | Nov 7 | Nov 19 | Nov 28 | Dec 5 | Dec 12 | Dec 19 | Dec 27 | Jan 6 | Jan 26 |
| First 32° | Oct 19 | Oct 27 | Nov 3 | Nov 8 | Nov 13 | Nov 18 | Nov 23 | Nov 30 | Dec 8 |
| First 36° | Oct 2 | Oct 9 | Oct 14 | Oct 19 | Oct 23 | Oct 28 | Nov 1 | Nov 7 | Nov 14 |
Data is provided by the NOAA National Centers for Environmental Information.