Frost Dates: First and last frost dates for beloit, wi

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for beloit, 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 24, and by October 18 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 29.
  2. There is a 50% chance of being hit by a 32° frost starting around October 9
  3. You have a 80% chance of seeing 32° by October 18
  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 9 Nov 14 Nov 18 Nov 21 Nov 24 Nov 27 Dec 1 Dec 5 Dec 10
First 20° Nov 4 Nov 8 Nov 11 Nov 14 Nov 16 Nov 19 Nov 21 Nov 24 Nov 28
First 24° Oct 23 Oct 28 Oct 31 Nov 3 Nov 6 Nov 9 Nov 12 Nov 15 Nov 20
First 28° Oct 8 Oct 14 Oct 18 Oct 21 Oct 24 Oct 28 Oct 31 Nov 4 Nov 10
First 32° Sep 24 Sep 29 Oct 3 Oct 6 Oct 9 Oct 12 Oct 15 Oct 18 Oct 23
First 36° Sep 23 Sep 26 Sep 29 Oct 1 Oct 3 Oct 5 Oct 7 Oct 10 Oct 13

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 May 20. 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 April 27, so we don't dare plant that early. We wait a few days and by May 6 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 4 Mar 28 Mar 24 Mar 20 Mar 16 Mar 12 Mar 8 Mar 3 Feb 25
Last 20° Apr 10 Apr 5 Apr 1 Mar 28 Mar 25 Mar 22 Mar 19 Mar 15 Mar 9
Last 24° Apr 15 Apr 11 Apr 8 Apr 6 Apr 3 Apr 1 Mar 30 Mar 27 Mar 23
Last 28° Apr 29 Apr 24 Apr 20 Apr 17 Apr 14 Apr 12 Apr 8 Apr 5 Mar 31
Last 32° May 8 May 2 Apr 29 Apr 26 Apr 23 Apr 20 Apr 16 Apr 13 Apr 8
Last 36° May 20 May 16 May 12 May 9 May 6 May 4 May 1 Apr 27 Apr 22

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