Frost Dates: First and last frost dates for Tracy Carbona, 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 April 27. 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 2, so we don't dare plant that early. We wait a few days and by March 24 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 11 | Jan 1 | Dec 20 | -- | -- | -- | -- | -- | -- |
| Last 28° | Feb 8 | Jan 31 | Jan 24 | Jan 19 | Jan 14 | Jan 9 | Jan 3 | Dec 26 | Dec 13 |
| Last 32° | Mar 19 | Mar 9 | Mar 1 | Feb 22 | Feb 16 | Feb 9 | Feb 3 | Jan 26 | Jan 15 |
| Last 36° | Apr 27 | Apr 16 | Apr 7 | Mar 31 | Mar 24 | Mar 18 | Mar 10 | Mar 2 | Feb 18 |
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 13.
- There is a 50% chance of being hit by a 32° frost starting around December 1
- You have a 80% chance of seeing 32° by December 20
- 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 18 | Dec 30 | Jan 12 | -- | -- | -- | -- | -- | -- |
| First 28° | Nov 28 | Dec 5 | Dec 11 | Dec 15 | Dec 20 | Dec 25 | Dec 30 | Jan 5 | Jan 17 |
| First 32° | Nov 3 | Nov 13 | Nov 20 | Nov 26 | Dec 1 | Dec 7 | Dec 13 | Dec 20 | Dec 29 |
| First 36° | Nov 1 | Nov 6 | Nov 9 | Nov 13 | Nov 16 | Nov 18 | Nov 22 | Nov 25 | Nov 30 |
Data is provided by the NOAA National Centers for Environmental Information.