Frost Dates: First and last frost dates for Hillsboro, ND

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 May 28, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
  • Around May 16, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
  • Before May 8, 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° Apr 13 Apr 8 Apr 5 Apr 1 Mar 30 Mar 27 Mar 24 Mar 20 Mar 15
Last 20° Apr 18 Apr 14 Apr 11 Apr 8 Apr 6 Apr 3 Apr 1 Mar 28 Mar 24
Last 24° Apr 27 Apr 23 Apr 20 Apr 17 Apr 15 Apr 12 Apr 10 Apr 7 Apr 2
Last 28° May 13 May 7 May 3 Apr 29 Apr 25 Apr 22 Apr 18 Apr 14 Apr 8
Last 32° May 19 May 15 May 12 May 9 May 7 May 4 May 1 Apr 28 Apr 24
Last 36° May 28 May 23 May 20 May 18 May 16 May 13 May 11 May 8 May 4

ℹ️ How to read these charts for the fall

As summer ends in Hillsboro, ND, 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 21, 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 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 October 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° Oct 23 Oct 28 Oct 31 Nov 3 Nov 6 Nov 9 Nov 11 Nov 15 Nov 20
First 20° Oct 11 Oct 17 Oct 21 Oct 25 Oct 28 Oct 31 Nov 4 Nov 8 Nov 13
First 24° Sep 29 Oct 4 Oct 9 Oct 12 Oct 15 Oct 19 Oct 22 Oct 26 Nov 1
First 28° Sep 21 Sep 26 Sep 30 Oct 3 Oct 6 Oct 9 Oct 12 Oct 16 Oct 21
First 32° Sep 18 Sep 21 Sep 24 Sep 26 Sep 28 Sep 30 Oct 2 Oct 5 Oct 8
First 36° Sep 4 Sep 9 Sep 12 Sep 15 Sep 18 Sep 21 Sep 23 Sep 27 Oct 1

📍 Frost Dates for other nearby locations

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