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

ℹ️ How to read these charts for the spring

As spring unfolds, the risk of frost gradually decreases each day until your tender plants are finally safe. The probabilities shown in the chart help you make smart decisions about when to plant.

While frost typically forms at 32°F, tender plants can be damaged even when temperatures are slightly higher. Air temperatures are often measured several feet above the ground, but temperatures at plant level can be several degrees colder. Protected areas like porches help by blocking radiational cooling. Given these variables, we consider 36°F the "caution zone" for frost-sensitive plants.

Key dates for your spring planting:

  • By August 5, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
  • Around July 29, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
  • Before July 23, there's still an 80% risk of frost — too early for tomatoes and other tender plants unless you're prepared to protect them

If the 10-day forecast shows no temperatures below 40°F, you might safely plant earlier than the above dates suggest. Many gardeners watch for this weather window to get a head start on the growing season.

In the Spring
Temperature 10% 20% 30% 40% 50% 60% 70% 80% 90%
Last 16° May 17 May 12 May 8 May 5 May 2 Apr 29 Apr 26 Apr 23 Apr 18
Last 20° Jun 3 May 29 May 24 May 21 May 18 May 14 May 11 May 6 May 1
Last 24° Jun 30 Jun 23 Jun 17 Jun 13 Jun 9 Jun 4 May 31 May 25 May 18
Last 28° Jul 28 Jul 19 Jul 12 Jul 7 Jul 1 Jun 26 Jun 20 Jun 14 Jun 5
Last 32° Aug 2 Jul 29 Jul 25 Jul 23 Jul 20 Jul 17 Jul 14 Jul 11 Jul 6
Last 36° Aug 5 Aug 3 Aug 1 Jul 30 Jul 29 Jul 27 Jul 25 Jul 23 Jul 21

ℹ️ How to read these charts for the fall

As summer ends in Wisdom, MT, nighttime temperatures begin to drop, and your risk of frost increases with each passing day. Knowing when to expect frost helps you harvest sensitive crops and extend your growing season with protection methods.

The chart below shows the probability of experiencing specific temperatures on various dates. Here's what this means for your garden:

1
Early warning: Around August 1, there's a 20% chance of 32°F — start monitoring forecasts and have plant covers ready
2
Decision time: By August 6, there's a 50% chance of frost — harvest tomatoes, peppers, and other tender crops or prepare protection
3
Last chance: By August 11, there's an 80% chance of seeing 32°F — most tender plants will be damaged without protection
4
Another perspective: You have only a 1 in 5 chance of making it past August 11 without a freezing night

These probabilities help you time your end-of-season harvests and know when to apply protective measures like row covers, cloches, or cold frames to extend your harvest.

In the Fall
Temperature 10% 20% 30% 40% 50% 60% 70% 80% 90%
First 16° Sep 5 Sep 10 Sep 13 Sep 17 Sep 19 Sep 22 Sep 25 Sep 29 Oct 4
First 20° Aug 28 Sep 1 Sep 5 Sep 8 Sep 10 Sep 13 Sep 16 Sep 19 Sep 23
First 24° Aug 17 Aug 22 Aug 25 Aug 28 Aug 31 Sep 3 Sep 6 Sep 9 Sep 14
First 28° Aug 6 Aug 10 Aug 13 Aug 16 Aug 19 Aug 21 Aug 24 Aug 27 Sep 1
First 32° Jul 30 Aug 1 Aug 3 Aug 4 Aug 6 Aug 7 Aug 9 Aug 11 Aug 13
First 36° Jul 31 Jul 31 Aug 1 Aug 2 Aug 2 Aug 3 Aug 4 Aug 5 Aug 6

📍 Frost Dates for other nearby locations

Or enter a new zipcode:

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