Frost Dates: First and last frost dates for san gabriel fire dept, 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 March 26. 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 January 24, so we don't dare plant that early. We wait a few days and by February 17 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° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 28° | Jan 22 | Jan 5 | -- | -- | -- | -- | -- | -- | -- |
| Last 32° | Feb 20 | Feb 7 | Jan 29 | Jan 20 | Jan 11 | Jan 2 | Dec 20 | -- | -- |
| Last 36° | Mar 26 | Mar 14 | Mar 5 | Feb 25 | Feb 17 | Feb 10 | Feb 2 | Jan 24 | Jan 11 |
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 December 12.
- There is a 50% chance of being hit by a 32° frost starting around January 5
- You have a 80% chance of seeing 32° by --
- 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° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| First 28° | Dec 30 | Jan 23 | -- | -- | -- | -- | -- | -- | -- |
| First 32° | Dec 1 | Dec 12 | Dec 21 | Dec 28 | Jan 5 | Jan 13 | Jan 25 | -- | -- |
| First 36° | Nov 10 | Nov 19 | Nov 25 | Nov 30 | Dec 5 | Dec 10 | Dec 16 | Dec 22 | Dec 31 |
Data is provided by the NOAA National Centers for Environmental Information.