Frost Dates: First and last frost dates for Cimarron, CO

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 23, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
  • Around July 8, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
  • Before June 29, 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 10 May 2 Apr 26 Apr 21 Apr 17 Apr 12 Apr 7 Apr 1 Mar 24
Last 20° May 29 May 21 May 15 May 10 May 5 Apr 30 Apr 25 Apr 19 Apr 11
Last 24° Jun 13 Jun 6 May 31 May 27 May 23 May 18 May 14 May 8 May 1
Last 28° Jun 19 Jun 14 Jun 9 Jun 6 Jun 3 May 30 May 27 May 22 May 17
Last 32° Jul 10 Jul 6 Jul 2 Jun 30 Jun 27 Jun 24 Jun 21 Jun 18 Jun 13
Last 36° Jul 23 Jul 18 Jul 14 Jul 11 Jul 8 Jul 6 Jul 3 Jun 29 Jun 24

ℹ️ How to read these charts for the fall

As summer ends in Cimarron, CO, 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 22, there's a 20% chance of 32°F — start monitoring forecasts and have plant covers ready
2
Decision time: By September 3, there's a 50% chance of frost — harvest tomatoes, peppers, and other tender crops or prepare protection
3
Last chance: By September 15, 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 15 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 9 Oct 13 Oct 16 Oct 20 Oct 23 Oct 28 Nov 3
First 20° Sep 21 Sep 26 Sep 29 Oct 2 Oct 4 Oct 7 Oct 9 Oct 12 Oct 17
First 24° Sep 15 Sep 19 Sep 22 Sep 24 Sep 27 Sep 29 Oct 1 Oct 4 Oct 8
First 28° Sep 4 Sep 9 Sep 13 Sep 16 Sep 19 Sep 21 Sep 24 Sep 28 Oct 3
First 32° Aug 15 Aug 22 Aug 26 Aug 30 Sep 3 Sep 6 Sep 10 Sep 15 Sep 21
First 36° Aug 1 Aug 7 Aug 12 Aug 16 Aug 20 Aug 24 Aug 28 Sep 1 Sep 8

📍 Frost Dates for other nearby locations

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