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 May 11. 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 March 28, so we don't dare plant that early. We wait a few days and by April 14 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 4 | Dec 12 | -- | -- | -- | -- | -- | -- | -- |
| Last 20° | Feb 7 | Jan 24 | Jan 13 | Jan 1 | Dec 15 | -- | -- | -- | -- |
| Last 24° | Mar 6 | Feb 20 | Feb 10 | Feb 1 | Jan 23 | Jan 14 | Jan 4 | Dec 23 | Nov 30 |
| Last 28° | Mar 28 | Mar 17 | Mar 8 | Mar 1 | Feb 22 | Feb 16 | Feb 9 | Jan 31 | Jan 19 |
| Last 32° | Apr 17 | Apr 8 | Apr 1 | Mar 26 | Mar 20 | Mar 14 | Mar 8 | Mar 1 | Feb 20 |
| Last 36° | May 11 | May 2 | Apr 25 | Apr 20 | Apr 14 | Apr 9 | Apr 4 | Mar 28 | Mar 19 |
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 17 | Jan 15 | -- | -- | -- | -- | -- | -- | -- |
| First 20° | Dec 9 | Dec 18 | Dec 26 | Jan 4 | Jan 18 | -- | -- | -- | -- |
| First 24° | Nov 21 | Nov 30 | Dec 6 | Dec 11 | Dec 17 | Dec 22 | Dec 28 | Jan 6 | -- |
| First 28° | Nov 5 | Nov 11 | Nov 15 | Nov 18 | Nov 21 | Nov 24 | Nov 27 | Dec 1 | Dec 6 |
| First 32° | Oct 29 | Nov 2 | Nov 6 | Nov 9 | Nov 12 | Nov 14 | Nov 17 | Nov 21 | Nov 26 |
| First 36° | Oct 19 | Oct 23 | Oct 27 | Oct 29 | Nov 1 | Nov 4 | Nov 7 | Nov 10 | Nov 14 |
Now that you know your frost dates, use our Garden Planting Calendar for Mojave, 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.
The Victory Seed Company is family owned and operated, working to help fellow gardeners succeed by selling popular vegetable, herb and flower seeds. Since the 1990s they have been heavily involved with the preservation of rare, open-pollinated, heirloom seeds. Visit them at www.VictorySeeds.com.
