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 June 29. 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 June 3, so we don't dare plant that early. We wait a few days and by June 13 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° | May 2 | Apr 18 | Apr 8 | Mar 31 | Mar 23 | Mar 15 | Mar 7 | Feb 25 | Feb 11 |
Last 20° | May 11 | May 1 | Apr 24 | Apr 18 | Apr 12 | Apr 6 | Mar 31 | Mar 24 | Mar 14 |
Last 24° | May 25 | May 17 | May 11 | May 5 | May 1 | Apr 26 | Apr 21 | Apr 15 | Apr 6 |
Last 28° | Jun 6 | May 30 | May 25 | May 20 | May 16 | May 12 | May 8 | May 3 | Apr 26 |
Last 32° | Jun 24 | Jun 17 | Jun 12 | Jun 8 | Jun 4 | May 31 | May 27 | May 22 | May 16 |
Last 36° | Jun 29 | Jun 23 | Jun 19 | Jun 16 | Jun 13 | Jun 10 | Jun 7 | Jun 3 | May 28 |
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° | Nov 10 | Nov 21 | Nov 28 | Dec 4 | Dec 10 | Dec 16 | Dec 22 | Dec 30 | Jan 9 |
First 20° | Oct 30 | Nov 7 | Nov 13 | Nov 18 | Nov 23 | Nov 27 | Dec 2 | Dec 8 | Dec 16 |
First 24° | Oct 13 | Oct 20 | Oct 26 | Oct 30 | Nov 4 | Nov 8 | Nov 12 | Nov 18 | Nov 25 |
First 28° | Oct 4 | Oct 11 | Oct 16 | Oct 21 | Oct 25 | Oct 29 | Nov 2 | Nov 7 | Nov 14 |
First 32° | Sep 19 | Sep 27 | Oct 2 | Oct 7 | Oct 11 | Oct 15 | Oct 20 | Oct 25 | Nov 2 |
First 36° | Sep 3 | Sep 10 | Sep 15 | Sep 19 | Sep 23 | Sep 27 | Oct 1 | Oct 6 | Oct 13 |
Now that you know your frost dates, use our Garden Planting Calendar for Grant Grove, 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.