Frost Dates: First and last frost dates for Pullman, WA

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 4, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
  • Around June 10, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
  • Before May 26, 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° Mar 2 Feb 22 Feb 16 Feb 11 Feb 6 Feb 1 Jan 27 Jan 20 Jan 7
Last 20° Mar 21 Mar 12 Mar 5 Feb 27 Feb 22 Feb 16 Feb 11 Feb 4 Jan 26
Last 24° Apr 16 Apr 6 Mar 30 Mar 24 Mar 19 Mar 13 Mar 7 Feb 28 Feb 19
Last 28° May 13 May 5 Apr 29 Apr 24 Apr 19 Apr 14 Apr 9 Apr 3 Mar 26
Last 32° May 31 May 24 May 20 May 16 May 12 May 8 May 4 Apr 29 Apr 22
Last 36° Jul 4 Jun 26 Jun 20 Jun 15 Jun 10 Jun 6 May 31 May 26 May 17

ℹ️ How to read these charts for the fall

As summer ends in Pullman, WA, 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 September 15, there's a 20% chance of 32°F — start monitoring forecasts and have plant covers ready
2
Decision time: By September 27, there's a 50% chance of frost — harvest tomatoes, peppers, and other tender crops or prepare protection
3
Last chance: By October 8, 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 October 8 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° Nov 4 Nov 13 Nov 21 Nov 27 Dec 3 Dec 9 Dec 15 Dec 24 Jan 9
First 20° Oct 17 Oct 27 Nov 3 Nov 10 Nov 15 Nov 21 Nov 27 Dec 5 Dec 15
First 24° Oct 3 Oct 11 Oct 17 Oct 22 Oct 27 Nov 1 Nov 6 Nov 12 Nov 21
First 28° Sep 20 Sep 26 Oct 1 Oct 4 Oct 8 Oct 11 Oct 15 Oct 20 Oct 26
First 32° Sep 9 Sep 15 Sep 19 Sep 23 Sep 27 Sep 30 Oct 4 Oct 8 Oct 14
First 36° Aug 24 Aug 30 Sep 3 Sep 7 Sep 10 Sep 13 Sep 16 Sep 20 Sep 26

📍 Frost Dates for other nearby locations

Or enter a new zipcode:

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