Frost Dates: First and last frost dates for Monterey, 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 24. 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 December 15, so we don't dare plant that early. We wait a few days and by January 30 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° | Dec 15 | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 32° | Jan 27 | Jan 14 | Jan 2 | Dec 18 | -- | -- | -- | -- | -- |
| Last 36° | Mar 24 | Mar 7 | Feb 22 | Feb 10 | Jan 30 | Jan 19 | Jan 5 | Dec 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 December 31.
- There is a 50% chance of being hit by a 32° frost starting around --
- 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° | Jan 16 | -- | -- | -- | -- | -- | -- | -- | -- |
| First 32° | Dec 18 | Dec 31 | Jan 13 | Jan 28 | -- | -- | -- | -- | -- |
| First 36° | Nov 21 | Dec 2 | Dec 10 | Dec 17 | Dec 24 | Dec 31 | Jan 9 | Jan 22 | -- |
Data is provided by the NOAA National Centers for Environmental Information.