Frost Dates: First and last frost dates for Philipsburg Rs, 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 July 29, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
  • Around July 17, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
  • Before July 9, 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 4 Apr 26 Apr 20 Apr 16 Apr 11 Apr 6 Apr 2 Mar 27 Mar 19
Last 20° May 15 May 9 May 5 May 1 Apr 27 Apr 24 Apr 20 Apr 16 Apr 10
Last 24° Jun 1 May 25 May 20 May 16 May 12 May 8 May 4 Apr 29 Apr 22
Last 28° Jun 29 Jun 21 Jun 15 Jun 10 Jun 6 Jun 1 May 27 May 21 May 13
Last 32° Jul 21 Jul 14 Jul 8 Jul 3 Jun 29 Jun 25 Jun 20 Jun 15 Jun 7
Last 36° Jul 29 Jul 25 Jul 22 Jul 19 Jul 17 Jul 15 Jul 12 Jul 9 Jul 5

ℹ️ How to read these charts for the fall

As summer ends in Philipsburg Rs, 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 16, there's a 20% chance of 32°F — start monitoring forecasts and have plant covers ready
2
Decision time: By August 26, there's a 50% chance of frost — harvest tomatoes, peppers, and other tender crops or prepare protection
3
Last chance: By September 5, 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 September 5 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 29 Oct 5 Oct 10 Oct 14 Oct 17 Oct 21 Oct 24 Oct 29 Nov 4
First 20° Sep 16 Sep 22 Sep 26 Sep 29 Oct 2 Oct 5 Oct 9 Oct 13 Oct 18
First 24° Sep 7 Sep 11 Sep 14 Sep 17 Sep 19 Sep 22 Sep 25 Sep 28 Oct 2
First 28° Aug 28 Sep 1 Sep 4 Sep 6 Sep 9 Sep 11 Sep 13 Sep 16 Sep 20
First 32° Aug 11 Aug 16 Aug 20 Aug 23 Aug 26 Aug 29 Sep 2 Sep 5 Sep 11
First 36° Aug 1 Aug 6 Aug 9 Aug 12 Aug 15 Aug 18 Aug 21 Aug 24 Aug 29

📍 Frost Dates for other nearby locations

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