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 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 February 9, so we don't dare plant that early. We wait a few days and by February 27 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. If conditions change and a surprise frost does threaten, there's always things you can do to protect plants from frost.
Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
---|---|---|---|---|---|---|---|---|---|
Last 16° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
Last 20° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
Last 24° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
Last 28° | Dec 11 | -- | -- | -- | -- | -- | -- | -- | -- |
Last 32° | Feb 19 | Feb 5 | Jan 25 | Jan 15 | Jan 4 | Dec 21 | -- | -- | -- |
Last 36° | Mar 27 | Mar 18 | Mar 11 | Mar 5 | Feb 27 | Feb 22 | Feb 16 | Feb 9 | Jan 30 |
The charts on this page show the probabilities of receiving a certain temperature on a certain day. Some examples that might help:
Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
---|---|---|---|---|---|---|---|---|---|
First 16° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
First 20° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
First 24° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
First 28° | Dec 18 | -- | -- | -- | -- | -- | -- | -- | -- |
First 32° | Nov 21 | Dec 3 | Dec 13 | Dec 22 | Dec 31 | Jan 12 | -- | -- | -- |
First 36° | Nov 8 | Nov 17 | Nov 23 | Nov 29 | Dec 4 | Dec 9 | Dec 15 | Dec 21 | Dec 30 |
Now that you know your frost dates, use our Garden Planting Calendar for Bloomington, California to know when to sow and transplant your various vegetable plants!
Data is provided by the NOAA National Centers for Environmental Information. Photography by Garden.org member TBGDN.