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

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Foxboro, 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 August 30, and by September 22 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 4.
  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 22
  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 17 Oct 21 Oct 25 Oct 28 Oct 31 Nov 3 Nov 6 Nov 9 Nov 14
First 20° Oct 4 Oct 10 Oct 14 Oct 17 Oct 20 Oct 24 Oct 27 Oct 31 Nov 6
First 24° Sep 21 Sep 27 Oct 1 Oct 5 Oct 8 Oct 12 Oct 15 Oct 20 Oct 26
First 28° Sep 15 Sep 19 Sep 21 Sep 23 Sep 25 Sep 27 Sep 30 Oct 2 Oct 5
First 32° Aug 30 Sep 4 Sep 7 Sep 10 Sep 13 Sep 15 Sep 18 Sep 22 Sep 27
First 36° Aug 13 Aug 19 Aug 23 Aug 27 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 3. 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 June 6, so we don't dare plant that early. We wait a few days and by June 17 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 15 Apr 12 Apr 9 Apr 6 Apr 3 Mar 31 Mar 26
Last 20° May 12 May 6 May 1 Apr 28 Apr 24 Apr 21 Apr 17 Apr 12 Apr 6
Last 24° May 30 May 23 May 19 May 15 May 11 May 7 May 3 Apr 28 Apr 22
Last 28° Jun 11 Jun 5 Jun 1 May 28 May 25 May 21 May 18 May 13 May 7
Last 32° Jun 27 Jun 20 Jun 15 Jun 11 Jun 7 Jun 3 May 30 May 25 May 18
Last 36° Jul 3 Jun 28 Jun 24 Jun 20 Jun 17 Jun 14 Jun 10 Jun 6 Jun 1

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