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 22. 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 26, so we don't dare plant that early. We wait a few days and by March 20 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° | Jan 24 | Jan 12 | Jan 3 | Dec 25 | Dec 14 | Nov 26 | -- | -- | -- |
| Last 28° | Feb 12 | Feb 1 | Jan 24 | Jan 16 | Jan 9 | Jan 2 | Dec 26 | Dec 16 | Nov 27 |
| Last 32° | Apr 6 | Mar 23 | Mar 13 | Mar 4 | Feb 23 | Feb 15 | Feb 6 | Jan 27 | Jan 13 |
| Last 36° | Apr 22 | Apr 10 | Apr 2 | Mar 26 | Mar 20 | Mar 13 | Mar 6 | Feb 26 | Feb 15 |
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° | Dec 5 | Dec 12 | Dec 18 | Dec 24 | Dec 31 | Jan 11 | -- | -- | -- |
| First 28° | Nov 15 | Nov 23 | Nov 28 | Dec 3 | Dec 8 | Dec 12 | Dec 18 | Dec 24 | Jan 6 |
| First 32° | Nov 5 | Nov 10 | Nov 14 | Nov 17 | Nov 20 | Nov 23 | Nov 27 | Nov 30 | Dec 6 |
| First 36° | Oct 23 | Oct 29 | Nov 2 | Nov 5 | Nov 8 | Nov 11 | Nov 15 | Nov 19 | Nov 24 |
Now that you know your frost dates, use our Garden Planting Calendar for Corcoran Irrig Dist, CA 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.
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