Frost Dates: First and last frost dates for Mitchell Caverns, 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 May 18. 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 March 30, so we don't dare plant that early. We wait a few days and by April 18 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 12 | Dec 29 | Dec 8 | -- | -- | -- | -- | -- |
| Last 24° | Feb 22 | Feb 6 | Jan 26 | Jan 14 | Jan 2 | Dec 15 | -- | -- | -- |
| Last 28° | Mar 25 | Mar 8 | Feb 23 | Feb 12 | Feb 2 | Jan 22 | Jan 9 | Dec 23 | -- |
| Last 32° | May 3 | Apr 20 | Apr 11 | Apr 3 | Mar 26 | Mar 19 | Mar 11 | Mar 1 | Feb 16 |
| Last 36° | May 18 | May 8 | May 1 | Apr 24 | Apr 18 | Apr 12 | Apr 6 | Mar 30 | Mar 19 |
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 8.
- There is a 50% chance of being hit by a 32° frost starting around November 24
- You have a 80% chance of seeing 32° by December 10
- 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 17 | Dec 31 | Jan 15 | -- | -- | -- | -- | -- | -- |
| First 24° | Nov 28 | Dec 13 | Dec 25 | Jan 6 | Jan 19 | Feb 11 | -- | -- | -- |
| First 28° | Nov 15 | Nov 24 | Nov 30 | Dec 6 | Dec 11 | Dec 17 | Dec 23 | Jan 2 | -- |
| First 32° | Oct 30 | Nov 8 | Nov 14 | Nov 19 | Nov 24 | Nov 29 | Dec 4 | Dec 10 | Dec 18 |
| First 36° | Oct 19 | Oct 27 | Nov 2 | Nov 7 | Nov 11 | Nov 16 | Nov 21 | Nov 26 | Dec 4 |
Data is provided by the NOAA National Centers for Environmental Information.