Frost Dates: First and last frost dates for Eagle River, WI

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Eagle River, 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 10, and by September 28 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 14.
  2. There is a 50% chance of being hit by a 32° frost starting around September 21
  3. You have a 80% chance of seeing 32° by September 28
  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 28 Nov 1 Nov 4 Nov 6 Nov 9 Nov 11 Nov 14 Nov 17 Nov 21
First 20° Oct 14 Oct 19 Oct 23 Oct 26 Oct 29 Nov 1 Nov 4 Nov 8 Nov 13
First 24° Sep 28 Oct 5 Oct 9 Oct 13 Oct 17 Oct 20 Oct 24 Oct 29 Nov 4
First 28° Sep 21 Sep 25 Sep 28 Sep 30 Oct 2 Oct 4 Oct 6 Oct 9 Oct 13
First 32° Sep 10 Sep 14 Sep 16 Sep 19 Sep 21 Sep 23 Sep 25 Sep 28 Oct 2
First 36° Aug 25 Aug 30 Sep 2 Sep 5 Sep 7 Sep 10 Sep 12 Sep 15 Sep 20

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 24. 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 31, so we don't dare plant that early. We wait a few days and by June 10 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 23 Apr 19 Apr 16 Apr 13 Apr 11 Apr 8 Apr 5 Apr 2 Mar 29
Last 20° May 5 Apr 30 Apr 26 Apr 23 Apr 20 Apr 17 Apr 13 Apr 9 Apr 4
Last 24° May 19 May 14 May 11 May 7 May 5 May 2 Apr 28 Apr 25 Apr 20
Last 28° May 31 May 27 May 23 May 20 May 18 May 15 May 12 May 8 May 4
Last 32° Jun 11 Jun 7 Jun 4 Jun 1 May 29 May 27 May 24 May 21 May 16
Last 36° Jun 24 Jun 19 Jun 16 Jun 13 Jun 10 Jun 7 Jun 4 May 31 May 26

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