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