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