Frost Dates: First and last frost dates for Marinette, WI

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Marinette, WI 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 September 20, and by October 13 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 25.
  2. There is a 50% chance of being hit by a 32° frost starting around October 4
  3. You have a 80% chance of seeing 32° by October 13
  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° Nov 3 Nov 9 Nov 13 Nov 16 Nov 20 Nov 23 Nov 27 Dec 1 Dec 6
First 20° Oct 24 Oct 30 Nov 3 Nov 6 Nov 10 Nov 13 Nov 16 Nov 20 Nov 26
First 24° Oct 12 Oct 19 Oct 23 Oct 27 Oct 31 Nov 4 Nov 8 Nov 13 Nov 20
First 28° Sep 30 Oct 6 Oct 11 Oct 14 Oct 18 Oct 22 Oct 26 Oct 30 Nov 5
First 32° Sep 20 Sep 25 Sep 28 Oct 1 Oct 4 Oct 7 Oct 9 Oct 13 Oct 17
First 36° Sep 9 Sep 14 Sep 17 Sep 20 Sep 23 Sep 26 Sep 29 Oct 3 Oct 8

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 7. 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 9, so we don't dare plant that early. We wait a few days and by May 20 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 11 Apr 6 Apr 2 Mar 30 Mar 28 Mar 25 Mar 22 Mar 18 Mar 13
Last 20° Apr 15 Apr 11 Apr 8 Apr 5 Apr 3 Mar 31 Mar 28 Mar 25 Mar 21
Last 24° Apr 28 Apr 23 Apr 19 Apr 16 Apr 13 Apr 10 Apr 7 Apr 4 Mar 30
Last 28° May 7 May 2 Apr 29 Apr 26 Apr 23 Apr 20 Apr 17 Apr 14 Apr 9
Last 32° May 19 May 15 May 12 May 10 May 7 May 5 May 3 Apr 30 Apr 26
Last 36° Jun 7 Jun 1 May 28 May 24 May 20 May 17 May 13 May 9 May 2

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