Frost Dates: First and last frost dates for dobbins, ca
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 June 1. 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 23, so we don't dare plant that early. We wait a few days and by May 8 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° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 20° | Jan 26 | Jan 10 | Dec 25 | -- | -- | -- | -- | -- | -- |
| Last 24° | Mar 17 | Feb 28 | Feb 15 | Feb 4 | Jan 25 | Jan 14 | Jan 2 | Dec 15 | -- |
| Last 28° | Apr 17 | Apr 1 | Mar 21 | Mar 12 | Mar 3 | Feb 22 | Feb 12 | Feb 1 | Jan 17 |
| Last 32° | May 11 | May 4 | Apr 29 | Apr 24 | Apr 20 | Apr 15 | Apr 11 | Apr 5 | Mar 29 |
| Last 36° | Jun 1 | May 24 | May 18 | May 13 | May 8 | May 3 | Apr 28 | Apr 23 | Apr 15 |
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 11
- You have a 80% chance of seeing 32° by November 25
- 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° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| First 20° | Dec 9 | Dec 27 | Jan 15 | -- | -- | -- | -- | -- | -- |
| First 24° | Nov 12 | Nov 26 | Dec 7 | Dec 15 | Dec 24 | Jan 2 | Jan 12 | Jan 26 | -- |
| First 28° | Nov 3 | Nov 13 | Nov 20 | Nov 25 | Dec 1 | Dec 6 | Dec 12 | Dec 19 | Dec 28 |
| First 32° | Oct 20 | Oct 27 | Nov 2 | Nov 6 | Nov 11 | Nov 15 | Nov 20 | Nov 25 | Dec 3 |
| First 36° | Oct 6 | Oct 12 | Oct 16 | Oct 19 | Oct 22 | Oct 26 | Oct 29 | Nov 2 | Nov 7 |
Data is provided by the NOAA National Centers for Environmental Information.