Frost Dates: First and last frost dates for Los Alamos, 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 12, so we don't dare plant that early. We wait a few days and by April 4 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° | Sep 6 | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 24° | Jan 27 | Dec 17 | Nov 3 | -- | -- | -- | -- | -- | -- |
| Last 28° | Mar 3 | Feb 4 | Jan 15 | Dec 25 | Dec 2 | Oct 22 | -- | -- | -- |
| Last 32° | Apr 16 | Mar 20 | Mar 1 | Feb 13 | Jan 29 | Jan 14 | Dec 29 | Dec 10 | Nov 14 |
| Last 36° | May 8 | Apr 27 | Apr 18 | Apr 11 | Apr 4 | Mar 28 | Mar 21 | Mar 12 | Mar 1 |
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 September 5.
- There is a 50% chance of being hit by a 32° frost starting around October 16
- You have a 80% chance of seeing 32° by November 26
- 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° | Nov 12 | -- | -- | -- | -- | -- | -- | -- | -- |
| First 24° | Sep 29 | Nov 17 | Jan 10 | -- | -- | -- | -- | -- | -- |
| First 28° | Sep 4 | Oct 2 | Oct 25 | Nov 16 | Dec 11 | Jan 25 | -- | -- | -- |
| First 32° | Aug 15 | Sep 5 | Sep 21 | Oct 4 | Oct 16 | Oct 28 | Nov 11 | Nov 26 | Dec 17 |
| First 36° | Aug 14 | Aug 26 | Sep 4 | Sep 11 | Sep 18 | Sep 25 | Oct 2 | Oct 11 | Oct 23 |
Data is provided by the NOAA National Centers for Environmental Information.