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