Frost Dates: First and last frost dates for ukiah, 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 11. 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 7, so we don't dare plant that early. We wait a few days and by April 20 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° | Dec 14 | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 24° | Jan 29 | Jan 18 | Jan 9 | Dec 31 | Dec 18 | -- | -- | -- | -- |
| Last 28° | Mar 10 | Feb 25 | Feb 16 | Feb 9 | Feb 1 | Jan 25 | Jan 17 | Jan 7 | Dec 23 |
| Last 32° | Apr 17 | Apr 7 | Mar 30 | Mar 24 | Mar 18 | Mar 12 | Mar 6 | Feb 27 | Feb 16 |
| Last 36° | May 11 | May 3 | Apr 28 | Apr 24 | Apr 20 | Apr 16 | Apr 12 | Apr 7 | Mar 30 |
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 4.
- There is a 50% chance of being hit by a 32° frost starting around November 16
- You have a 80% chance of seeing 32° by November 28
- 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° | Jan 16 | -- | -- | -- | -- | -- | -- | -- | -- |
| First 24° | Dec 3 | Dec 17 | Dec 29 | Jan 11 | Feb 2 | -- | -- | -- | -- |
| First 28° | Nov 7 | Nov 18 | Nov 26 | Dec 3 | Dec 10 | Dec 17 | Dec 24 | Jan 2 | Jan 16 |
| First 32° | Oct 29 | Nov 4 | Nov 9 | Nov 13 | Nov 16 | Nov 20 | Nov 24 | Nov 28 | Dec 5 |
| First 36° | Oct 22 | Oct 25 | Oct 28 | Oct 30 | Nov 2 | Nov 4 | Nov 6 | Nov 9 | Nov 13 |
Data is provided by the NOAA National Centers for Environmental Information.