Frost Dates: First and last frost dates for Mc Call, ID

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 29. 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 July 9, so we don't dare plant that early. We wait a few days and by July 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 27 Apr 20 Apr 14 Apr 10 Apr 6 Apr 2 Mar 29 Mar 23 Mar 16
Last 20° May 12 May 6 May 2 Apr 28 Apr 25 Apr 21 Apr 18 Apr 13 Apr 7
Last 24° Jun 18 Jun 8 May 31 May 25 May 19 May 13 May 6 Apr 29 Apr 19
Last 28° Jun 30 Jun 23 Jun 18 Jun 14 Jun 10 Jun 6 Jun 2 May 28 May 21
Last 32° Jul 17 Jul 11 Jul 8 Jul 4 Jul 1 Jun 28 Jun 25 Jun 21 Jun 16
Last 36° Jul 29 Jul 25 Jul 22 Jul 19 Jul 17 Jul 15 Jul 12 Jul 9 Jul 5

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Mc Call, ID 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 5, and by September 5 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 August 11.
  2. There is a 50% chance of being hit by a 32° frost starting around August 24
  3. You have a 80% chance of seeing 32° by September 5
  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 1 Oct 8 Oct 13 Oct 17 Oct 21 Oct 25 Oct 29 Nov 3 Nov 10
First 20° Sep 13 Sep 20 Sep 24 Sep 28 Oct 2 Oct 6 Oct 10 Oct 15 Oct 21
First 24° Sep 3 Sep 8 Sep 12 Sep 16 Sep 19 Sep 22 Sep 26 Sep 30 Oct 5
First 28° Aug 22 Aug 27 Aug 31 Sep 3 Sep 6 Sep 9 Sep 13 Sep 16 Sep 22
First 32° Aug 5 Aug 11 Aug 16 Aug 20 Aug 24 Aug 27 Aug 31 Sep 5 Sep 11
First 36° Jul 31 Aug 4 Aug 8 Aug 11 Aug 14 Aug 17 Aug 20 Aug 24 Aug 29

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