Frost Dates: First and last frost dates for Sandy Lake Dam Libby, MN
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 14.
- There is a 50% chance of being hit by a 32° frost starting around September 23
- You have a 80% chance of seeing 32° by October 3
- 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 24 | Oct 29 | Nov 1 | Nov 4 | Nov 6 | Nov 9 | Nov 12 | Nov 15 | Nov 19 |
First 20° | Oct 14 | Oct 19 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 4 | Nov 8 | Nov 13 |
First 24° | Oct 5 | Oct 11 | Oct 14 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 30 | Nov 4 |
First 28° | Sep 16 | Sep 21 | Sep 24 | Sep 27 | Sep 30 | Oct 3 | Oct 6 | Oct 9 | Oct 14 |
First 32° | Sep 8 | Sep 14 | Sep 17 | Sep 20 | Sep 23 | Sep 26 | Sep 29 | Oct 3 | Oct 8 |
First 36° | Aug 29 | Sep 3 | Sep 7 | Sep 10 | Sep 13 | Sep 16 | Sep 19 | Sep 23 | Sep 28 |
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 13. 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 15, so we don't dare plant that early. We wait a few days and by May 27 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 16 | Apr 12 | Apr 9 | Apr 7 | Apr 5 | Apr 2 | Mar 31 | Mar 28 | Mar 24 |
Last 20° | Apr 24 | Apr 20 | Apr 17 | Apr 14 | Apr 12 | Apr 10 | Apr 7 | Apr 4 | Mar 31 |
Last 24° | May 5 | Apr 30 | Apr 27 | Apr 24 | Apr 22 | Apr 19 | Apr 16 | Apr 13 | Apr 9 |
Last 28° | May 15 | May 10 | May 7 | May 4 | May 2 | Apr 30 | Apr 27 | Apr 24 | Apr 19 |
Last 32° | May 26 | May 21 | May 18 | May 15 | May 12 | May 9 | May 6 | May 3 | Apr 28 |
Last 36° | Jun 13 | Jun 7 | Jun 3 | May 30 | May 27 | May 23 | May 20 | May 15 | May 10 |
Data is provided by the NOAA National Centers for Environmental Information.