Frost Dates: First and last frost dates for Plain, 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 11, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
  • Around June 23, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
  • Before June 11, 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 20 Mar 12 Mar 6 Mar 1 Feb 24 Feb 19 Feb 14 Feb 8 Jan 31
Last 20° Apr 6 Mar 29 Mar 24 Mar 19 Mar 14 Mar 9 Mar 4 Feb 27 Feb 19
Last 24° Apr 30 Apr 23 Apr 19 Apr 15 Apr 12 Apr 8 Apr 5 Mar 31 Mar 25
Last 28° May 26 May 20 May 16 May 13 May 10 May 7 May 3 Apr 30 Apr 24
Last 32° Jun 18 Jun 11 Jun 6 Jun 2 May 29 May 25 May 21 May 16 May 10
Last 36° Jul 11 Jul 5 Jul 1 Jun 27 Jun 23 Jun 19 Jun 15 Jun 11 Jun 5

ℹ️ How to read these charts for the fall

As summer ends in Plain, 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 5, there's a 20% chance of 32°F — start monitoring forecasts and have plant covers ready
2
Decision time: By September 15, there's a 50% chance of frost — harvest tomatoes, peppers, and other tender crops or prepare protection
3
Last chance: By September 24, 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 24 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 2 Nov 11 Nov 17 Nov 23 Nov 28 Dec 3 Dec 8 Dec 14 Dec 23
First 20° Oct 18 Oct 27 Nov 2 Nov 7 Nov 13 Nov 18 Nov 23 Nov 29 Dec 8
First 24° Oct 3 Oct 8 Oct 12 Oct 15 Oct 19 Oct 22 Oct 25 Oct 29 Nov 3
First 28° Sep 16 Sep 20 Sep 23 Sep 25 Sep 28 Sep 30 Oct 2 Oct 5 Oct 9
First 32° Sep 1 Sep 5 Sep 9 Sep 12 Sep 15 Sep 18 Sep 21 Sep 24 Sep 29
First 36° Aug 22 Aug 26 Aug 29 Aug 31 Sep 3 Sep 5 Sep 8 Sep 10 Sep 15

📍 Frost Dates for other nearby locations

Or enter a new zipcode:

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