Will there be an early or late frost? InkFreeNews photo from coldclimategardening.com

By Jeff Burbrink
Extension Educator, Purdue Extension Elkhart County

Jeff Burbrink
Extension Educator, Purdue University Elkhart County

ELKHART COUNTY — Last week, someone asked me if our frost was arriving late this year, so I started sifting through data collected by the various weather services.

Light frost can occur when the temperature falls below 36°F, especially in lower spots in rural areas, like muck ground.  Frost becomes more widespread when the temperature falls to 32°F with some freeze possible in the low areas. 32°F has generally been adopted as the universal “first frost” temperature. The definition of a hard freeze is temperatures below 28°F, which results in the killing most of the remaining tender plants at that point.

The Elkhart County fall frost and freeze data for the latest 30-year averages as compiled by the Midwest Regional Climate Center averages are:

First Frost of Fall (1980 – current)

Earliest First 32°F – Sept. 21-30

Median First 32°F – October 11-20

Latest First 32°F – Nov. 11-20

First Hard Freeze of Fall (1980-current)

Earliest First 28°F – Oct. 1-10

Median First 28°F – Nov. 1-10

Latest First 28°F – Nov. 21-30

Being a bit of a weather nerd, I wanted to know how our current spring frost and freeze data compare to the past. I dug out an old 1981 publication by Purdue’s James Newman to see how the frost and freeze dates compare. In 1981, the 30-year median 32°F first fall frost fell between Oct. 6-10 in Elkhart County, and the 30-year median 28°F first fall hard freeze was Oct. 15-20. It appears our average growing season is about a week longer now in the fall than it was just 30 years ago.

With my curiosity peeked now, I decided to see how the spring frosts and freezes have changed.

Last Frost of Spring (1980-current)

Earliest Last 32°F – April 1-10

Median Last 32°F – April 21-30

Latest Last 32°F – May 21-30

Last Hard Freeze of Spring (1980-current)

Earliest Last 28°F – March 21-31

Median Last 28°F – April 11-20

Latest Last 28°F – May 1-10

Purdue’s 1981 publication says the last 32°F temperature in the spring Elkhart County averaged May 6-10. The last 28°F hard freeze in spring of 1981 averaged April 21-25. So, we have gained 10-12 extra days in the spring on average.

According to Purdue’s 1981 publication, the 30-year median 32°F last spring frost fell between May 6-10 in Elkhart County, and the 30-year median 28°F last spring hard freeze was April 21-25. It appears our average growing season starts about a week earlier than it was just 30 years ago.

I ran this information past Leland Shaum, another self-professed local weather enthusiast. He and his wife Sharon collect local weather data for the National Weather Service. They went through great lengths to digitize hand written weather data collected by Goshen College’s S.W. Witmer, Lores Steury, and several others, dating back to 1915, making it easier to crunch the numbers. Sure enough, those records indicate our growing season has lengthened every decade, both in the spring and in the fall. Shaum estimates our growing season is now 23 days longer on average than it was in 1915. Fascinating.

It looks like we will be waiting a while longer for our first frost and freeze of 2021. As of today (Oct. 18), there are still no 32°F temperatures predicted for Elkhart County by the National Weather Service through Oct. 25.