Frost Dates: First and last frost dates for Ojai, 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 8. 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 24, so we don't dare plant that early. We wait a few days and by April 11 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° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 24° | Jan 15 | Dec 30 | Dec 12 | -- | -- | -- | -- | -- | -- |
| Last 28° | Feb 17 | Feb 6 | Jan 28 | Jan 20 | Jan 13 | Jan 5 | Dec 28 | Dec 16 | -- |
| Last 32° | Apr 9 | Mar 28 | Mar 20 | Mar 12 | Mar 5 | Feb 26 | Feb 19 | Feb 10 | Jan 29 |
| Last 36° | May 8 | Apr 29 | Apr 22 | Apr 16 | Apr 11 | Apr 5 | Mar 31 | Mar 24 | Mar 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 November 7.
- There is a 50% chance of being hit by a 32° frost starting around November 23
- 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° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| First 24° | Dec 16 | Dec 30 | Jan 15 | -- | -- | -- | -- | -- | -- |
| First 28° | Nov 21 | Nov 29 | Dec 6 | Dec 11 | Dec 16 | Dec 22 | Dec 29 | Jan 8 | -- |
| First 32° | Oct 29 | Nov 7 | Nov 13 | Nov 18 | Nov 23 | Nov 28 | Dec 4 | Dec 10 | Dec 18 |
| First 36° | Oct 21 | Oct 27 | Nov 1 | Nov 4 | Nov 8 | Nov 12 | Nov 15 | Nov 20 | Nov 26 |
Data is provided by the NOAA National Centers for Environmental Information.