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

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for laona, 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 3, and by September 27 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 8.
  2. There is a 50% chance of being hit by a 32° frost starting around September 17
  3. You have a 80% chance of seeing 32° by September 27
  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 22 Oct 27 Oct 31 Nov 3 Nov 6 Nov 9 Nov 12 Nov 16 Nov 21
First 20° Oct 15 Oct 20 Oct 24 Oct 27 Oct 30 Nov 2 Nov 5 Nov 8 Nov 13
First 24° Sep 29 Oct 5 Oct 9 Oct 12 Oct 16 Oct 19 Oct 22 Oct 27 Nov 1
First 28° Sep 17 Sep 22 Sep 25 Sep 28 Oct 1 Oct 4 Oct 7 Oct 11 Oct 16
First 32° Sep 3 Sep 8 Sep 12 Sep 15 Sep 17 Sep 20 Sep 23 Sep 27 Oct 1
First 36° Aug 19 Aug 25 Aug 30 Sep 3 Sep 7 Sep 11 Sep 15 Sep 20 Sep 26

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 1. 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 12 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 21 Apr 16 Apr 13 Apr 10 Apr 7 Apr 4 Apr 1 Mar 29 Mar 24
Last 20° May 2 Apr 27 Apr 24 Apr 20 Apr 18 Apr 15 Apr 11 Apr 8 Apr 3
Last 24° May 11 May 6 May 3 Apr 30 Apr 27 Apr 24 Apr 21 Apr 18 Apr 13
Last 28° May 31 May 26 May 21 May 18 May 15 May 11 May 8 May 3 Apr 28
Last 32° Jun 18 Jun 13 Jun 8 Jun 5 Jun 1 May 29 May 25 May 21 May 15
Last 36° Jul 1 Jun 25 Jun 20 Jun 16 Jun 12 Jun 9 Jun 5 May 31 May 25

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