Frost Dates: First and last frost dates for cass lake, mn

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for cass lake, 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 29, and by September 23 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 3.
  2. There is a 50% chance of being hit by a 32° frost starting around September 13
  3. You have a 80% chance of seeing 32° by September 23
  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 12 Oct 18 Oct 22 Oct 25 Oct 29 Nov 1 Nov 4 Nov 9 Nov 14
First 20° Sep 29 Oct 5 Oct 9 Oct 13 Oct 16 Oct 19 Oct 23 Oct 27 Nov 2
First 24° Sep 20 Sep 25 Sep 29 Oct 2 Oct 5 Oct 8 Oct 12 Oct 15 Oct 21
First 28° Sep 13 Sep 17 Sep 20 Sep 23 Sep 25 Sep 28 Sep 30 Oct 3 Oct 7
First 32° Aug 29 Sep 3 Sep 7 Sep 10 Sep 13 Sep 16 Sep 19 Sep 23 Sep 28
First 36° Aug 13 Aug 18 Aug 23 Aug 26 Aug 29 Sep 1 Sep 5 Sep 9 Sep 14

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 June 28. 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 28, so we don't dare plant that early. We wait a few days and by June 9 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 27 Apr 23 Apr 19 Apr 17 Apr 14 Apr 11 Apr 9 Apr 5 Apr 1
Last 20° May 12 May 7 May 3 Apr 29 Apr 26 Apr 23 Apr 19 Apr 15 Apr 10
Last 24° May 16 May 12 May 9 May 6 May 4 May 2 Apr 29 Apr 26 Apr 22
Last 28° May 26 May 22 May 19 May 17 May 15 May 12 May 10 May 7 May 3
Last 32° Jun 10 Jun 5 Jun 1 May 29 May 26 May 23 May 20 May 16 May 11
Last 36° Jun 28 Jun 21 Jun 17 Jun 13 Jun 9 Jun 5 Jun 1 May 28 May 21

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