Frost Dates: First and last frost dates for Neihart, MT

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 26. 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 27, so we don't dare plant that early. We wait a few days and by July 9 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 29 Apr 23 Apr 19 Apr 16 Apr 13 Apr 9 Apr 6 Apr 2 Mar 27
Last 20° May 9 May 3 Apr 29 Apr 25 Apr 22 Apr 19 Apr 15 Apr 11 Apr 5
Last 24° May 19 May 14 May 11 May 8 May 5 May 2 Apr 29 Apr 26 Apr 21
Last 28° Jun 12 Jun 6 Jun 1 May 28 May 24 May 21 May 17 May 12 May 6
Last 32° Jul 8 Jul 1 Jun 25 Jun 20 Jun 16 Jun 12 Jun 7 Jun 1 May 25
Last 36° Jul 26 Jul 20 Jul 16 Jul 12 Jul 9 Jul 5 Jul 2 Jun 27 Jun 21

How to read these charts for the fall
As your growing season comes to an end, the nightly temperatures for Neihart, MT 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 19, and by September 17 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 25.
  2. There is a 50% chance of being hit by a 32° frost starting around September 5
  3. You have a 80% chance of seeing 32° by September 17
  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° Sep 30 Oct 5 Oct 10 Oct 13 Oct 17 Oct 20 Oct 24 Oct 28 Nov 3
First 20° Sep 20 Sep 26 Sep 30 Oct 4 Oct 7 Oct 10 Oct 14 Oct 18 Oct 24
First 24° Sep 14 Sep 19 Sep 23 Sep 26 Sep 29 Oct 2 Oct 6 Oct 10 Oct 15
First 28° Sep 4 Sep 9 Sep 12 Sep 14 Sep 17 Sep 19 Sep 22 Sep 25 Sep 29
First 32° Aug 19 Aug 25 Aug 29 Sep 2 Sep 5 Sep 9 Sep 12 Sep 17 Sep 23
First 36° Aug 3 Aug 9 Aug 13 Aug 17 Aug 20 Aug 24 Aug 28 Sep 1 Sep 7

Frost Dates for other nearby locations
  • Raynesford, MT
  • Stanford, MT
  • Martinsdale, MT
  • Lennep, MT
  • Shonkin, MT
  • Moccasin, MT
  • Geraldine, MT
  • Great Falls, MT
  • Cascade, MT
  • Denton, MT

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