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