Frost Dates: First and last frost dates for Sonnette, MT
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 12. 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 22 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.
Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
---|---|---|---|---|---|---|---|---|---|
Last 16° | Apr 22 | Apr 17 | Apr 13 | Apr 10 | Apr 7 | Apr 4 | Mar 31 | Mar 28 | Mar 22 |
Last 20° | May 6 | Apr 30 | Apr 26 | Apr 22 | Apr 19 | Apr 15 | Apr 12 | Apr 8 | Apr 2 |
Last 24° | May 15 | May 11 | May 7 | May 5 | May 2 | Apr 29 | Apr 27 | Apr 23 | Apr 19 |
Last 28° | May 30 | May 24 | May 20 | May 16 | May 13 | May 10 | May 7 | May 2 | Apr 27 |
Last 32° | Jun 16 | Jun 10 | Jun 6 | Jun 2 | May 30 | May 27 | May 23 | May 19 | May 13 |
Last 36° | Jul 12 | Jul 5 | Jun 30 | Jun 26 | Jun 22 | Jun 18 | 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:
- You have a small 20% chance of getting 32° by September 6.
- There is a 50% chance of being hit by a 32° frost starting around September 13
- You have a 80% chance of seeing 32° by September 20
- Said another way, you have a 1 in 5 chance at making it to that day without a 32° night.
Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
---|---|---|---|---|---|---|---|---|---|
First 16° | Oct 5 | Oct 12 | Oct 17 | Oct 21 | Oct 24 | Oct 28 | Nov 1 | Nov 6 | Nov 12 |
First 20° | Sep 26 | Oct 2 | Oct 7 | Oct 10 | Oct 14 | Oct 17 | Oct 21 | Oct 25 | Oct 31 |
First 24° | Sep 16 | Sep 21 | Sep 25 | Sep 29 | Oct 2 | Oct 5 | Oct 9 | Oct 13 | Oct 19 |
First 28° | Sep 9 | Sep 13 | Sep 15 | Sep 18 | Sep 20 | Sep 23 | Sep 25 | Sep 28 | Oct 2 |
First 32° | Sep 2 | Sep 6 | Sep 9 | Sep 11 | Sep 13 | Sep 15 | Sep 17 | Sep 20 | Sep 24 |
First 36° | Aug 15 | Aug 21 | Aug 25 | Aug 29 | Sep 1 | Sep 5 | Sep 8 | Sep 13 | Sep 19 |
Data is provided by the NOAA National Centers for Environmental Information.