Frost Dates: First and last frost dates for Thorhult, MN

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Thorhult, MN start to go down, and therefore every day that goes by increases the chance that you'll get frost. Your risk of frost really begins around August 28, and by September 20 you're almost certain to have received at least one frost event.

The charts on this page show the probabilities of receiving a certain temperature on a certain day. Some examples that might help:

  1. You have a small 20% chance of getting 32° by September 2.
  2. There is a 50% chance of being hit by a 32° frost starting around September 11
  3. You have a 80% chance of seeing 32° by September 20
  4. Said another way, you have a 1 in 5 chance at making it to that day without a 32° night.
In the Fall
Temperature 10% 20% 30% 40% 50% 60% 70% 80% 90%
First 16° Oct 6 Oct 13 Oct 18 Oct 22 Oct 26 Oct 29 Nov 3 Nov 7 Nov 14
First 20° Sep 29 Oct 5 Oct 9 Oct 13 Oct 17 Oct 20 Oct 24 Oct 28 Nov 3
First 24° Sep 19 Sep 24 Sep 28 Oct 1 Oct 4 Oct 7 Oct 10 Oct 13 Oct 18
First 28° Sep 6 Sep 11 Sep 15 Sep 18 Sep 20 Sep 23 Sep 26 Sep 29 Oct 4
First 32° Aug 28 Sep 2 Sep 5 Sep 8 Sep 11 Sep 14 Sep 17 Sep 20 Sep 25
First 36° Aug 13 Aug 18 Aug 23 Aug 26 Aug 30 Sep 2 Sep 6 Sep 10 Sep 16

How to read these charts for the spring
As the growing season approaches, the days get longer, the weather begins to warm up, and the nights start being less cold. You're still getting frost, but the chance of nightly frosts gets less and less with each passing day. Eventually, the frost stops, and this is when your tender plants are fully safe. So, how do you plan for this? The probabilities on this page help you assess your risk of frost on any given day.

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 6. 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 27, so we don't dare plant that early. We wait a few days and by June 12 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.

In the Spring
Temperature 10% 20% 30% 40% 50% 60% 70% 80% 90%
Last 16° Apr 21 Apr 16 Apr 13 Apr 11 Apr 8 Apr 5 Apr 3 Mar 31 Mar 26
Last 20° May 5 Apr 29 Apr 25 Apr 22 Apr 19 Apr 15 Apr 12 Apr 8 Apr 2
Last 24° May 16 May 11 May 7 May 4 May 1 Apr 27 Apr 24 Apr 20 Apr 15
Last 28° May 27 May 22 May 19 May 16 May 13 May 10 May 8 May 4 Apr 29
Last 32° Jun 15 Jun 9 Jun 5 Jun 1 May 29 May 25 May 22 May 17 May 11
Last 36° Jul 6 Jun 28 Jun 22 Jun 17 Jun 12 Jun 7 Jun 2 May 27 May 19

Data is provided by the NOAA National Centers for Environmental Information.