Frost Dates: First and last frost dates for Sandberg, 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 21, so we don't dare plant that early. We wait a few days and by May 7 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 27 | Jan 7 | Dec 11 | -- | -- | -- | -- | -- | -- |
| Last 20° | Feb 5 | Jan 21 | Jan 7 | Dec 21 | -- | -- | -- | -- | -- |
| Last 24° | Apr 3 | Mar 13 | Feb 25 | Feb 10 | Jan 24 | Jan 3 | -- | -- | -- |
| Last 28° | May 3 | Apr 16 | Apr 4 | Mar 24 | Mar 14 | Mar 5 | Feb 22 | Feb 10 | Jan 24 |
| Last 32° | May 24 | May 13 | May 5 | Apr 28 | Apr 21 | Apr 14 | Apr 7 | Mar 30 | Mar 19 |
| Last 36° | Jun 1 | May 24 | May 18 | May 12 | May 7 | May 3 | Apr 27 | Apr 21 | Apr 13 |
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 November 6.
- There is a 50% chance of being hit by a 32° frost starting around November 19
- You have a 80% chance of seeing 32° by December 2
- 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 25 | Jan 15 | -- | -- | -- | -- | -- | -- | -- |
| First 20° | Dec 13 | Dec 27 | Jan 10 | Jan 30 | -- | -- | -- | -- | -- |
| First 24° | Nov 16 | Dec 1 | Dec 12 | Dec 23 | Jan 5 | Jan 22 | -- | -- | -- |
| First 28° | Nov 4 | Nov 14 | Nov 21 | Nov 27 | Dec 3 | Dec 9 | Dec 15 | Dec 22 | Jan 1 |
| First 32° | Oct 30 | Nov 6 | Nov 11 | Nov 15 | Nov 19 | Nov 23 | Nov 27 | Dec 2 | Dec 9 |
| First 36° | Oct 12 | Oct 19 | Oct 24 | Oct 28 | Nov 1 | Nov 5 | Nov 10 | Nov 15 | Nov 22 |
Data is provided by the NOAA National Centers for Environmental Information.