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