Frost Dates: First and last frost dates for Callahan, CA

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 9, 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 13, 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 4 Feb 19 Feb 9 Feb 1 Jan 24 Jan 15 Jan 5 Dec 23 --
Last 20° Apr 4 Mar 23 Mar 15 Mar 7 Feb 28 Feb 21 Feb 14 Feb 5 Jan 24
Last 24° Apr 30 Apr 22 Apr 16 Apr 12 Apr 7 Apr 3 Mar 29 Mar 24 Mar 16
Last 28° May 28 May 22 May 17 May 13 May 10 May 6 May 3 Apr 28 Apr 22
Last 32° Jun 23 Jun 16 Jun 10 Jun 5 Jun 1 May 28 May 23 May 18 May 10
Last 36° Jul 9 Jul 3 Jun 29 Jun 26 Jun 23 Jun 20 Jun 17 Jun 13 Jun 7

ℹ️ How to read these charts for the fall

As summer ends in Callahan, CA, 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 18, there's a 20% chance of 32°F — start monitoring forecasts and have plant covers ready
2
Decision time: By September 28, there's a 50% chance of frost — harvest tomatoes, peppers, and other tender crops or prepare protection
3
Last chance: By October 9, 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 9 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 15 Nov 24 Dec 1 Dec 7 Dec 12 Dec 18 Dec 25 Jan 3 --
First 20° Nov 5 Nov 11 Nov 16 Nov 20 Nov 24 Nov 28 Dec 2 Dec 6 Dec 13
First 24° Oct 19 Oct 25 Oct 29 Nov 2 Nov 5 Nov 8 Nov 12 Nov 16 Nov 22
First 28° Oct 3 Oct 9 Oct 13 Oct 17 Oct 20 Oct 23 Oct 27 Oct 31 Nov 5
First 32° Sep 12 Sep 18 Sep 22 Sep 25 Sep 28 Oct 1 Oct 5 Oct 9 Oct 14
First 36° Aug 22 Aug 29 Sep 4 Sep 8 Sep 12 Sep 17 Sep 21 Sep 26 Oct 4

📍 Frost Dates for other nearby locations

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