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