Back in the 1960s, the United States Department of Agriculture produced a map of the nation with a number of hardiness zones to help guide gardeners and landscapers with better planting advice.

However, those early maps don’t reflect the same zones as today’s maps. There are no doubt, warmer, albeit slightly, patterns that are moving farther north. In fact, when you take North Dakota into account, there have been some major changes since 1990.

It’s the same with Manitoba and Saskatchewan, which border North Dakota to the north. Their zones, created in 1970, have changed one hardiness zone.

Here in the United States, hardiness zones are categorized from zero to 12 and within each zone there is an A and B zone. All of North Dakota is within either zone 3 or zone 4. But what is interesting about this is there are small pockets of the state that might surprise you.

We all know it can get what we call “bitter cold” in the winter. Since February 1996, I’ve seen three mornings drop to 40 and 41 below zero without the wind chill. I remember these mornings because extreme cold fascinates me more than I’m afraid of it. Two of those mornings were consecutive when I lived in Langdon and the other happened on a trip from Bismarck to Carpio.
But we also know that North Dakota can have wild swings in temperatures. I’ve also witnessed an extreme high of 114 above zero, which was in Hazelton when I was growing up in the late ‘60s.

Many of us talk about these extremes and make the assumption that if we have an unusually cold winter or extremely hot summer, That’s our zone. We have to remember, those are extremes and our hardiness zone isn’t based solely on the bottom of the Fahrenheit scale, although that’s part of the equation.

The coldest zone in North Dakota is Zone 3A, which is almost exclusively in Bottineau County. Long-term extremes are listed as 35 to 40 below zero. It tends to follow the Souris River valley south, just touching the northern tip of McHenry County. There’s also a 3A pocket in the southeast corner of Bottineau County, in the Willow City area.

Nearly all of the rest of the northern tier of North Dakota, at least above U.S. Highway 2, is Zone 3B, which is listed at 30 to 35 below, meaning every winter will probably drop to those temperatures.

The gooseneck of Ward County is interesting because that narrow piece of property takes in two hardiness zones. Carpio and Minot are considered Zone 4A, but just eight miles up the road from Carpio, in Donnybrook, we fall into Zone 3B. Kenmare is also 3B.

Again, there are pockets of 3B elsewhere in the state surrounded by Zone 4, which emcompasses most of the rest of the state. Southeast of Williston, nearly all of Nelson County, a small area south of Beulah, and here’s a real surprise, the extreme southern part of Morton County, south of Flasher, are all Zone 3B.

What makes that spot south of Flasher really interesting is that less than 30 miles south of there, near Fort Yates which is in Sioux County, there is a pocket of Zone 4B, which is described as 20 to 25 below for long-term extremes.

Another 4B pocket exists west of there, straddling the Sioux/Adams County line, which is just to the east of Hettinger. There is one more 4B pocket and that is in western LaMoure County, which is the Edgeley area, but not reaching Kulm, 15 miles west or LaMoure, 20 miles east.

There are no Zone 5A areas in North Dakota, but by the time you get south of Pierre, S.D., most of that part of South Dakota is Zone 5A, including Rapid City and Sturgis.

Back to those early maps; most of northeastern North Dakota, starting from Minot east to the Minnesota border and south into the Devils Lake Basin, was all Zone 2, with the rest of North Dakota being Zone 3.

By 1990, all of that had changed. The entire Red River Valley, including Pembina and Drayton, were now classified as Zone 4, with a couple of more spots around Jamestown and Cooperstown and the U.S. Highway 83 corridor, north almost to Minot.
Changes in Alaska are also quite dramatic. Up until 1980, nearly the entire state was 2A or below. By 2010, nearly the entire state, including Prudoe Bay and Point Barrow along the North Slope, had become 3A and 3B, with a large swath north of Achorage now 4B. That means most of northern Alaska has the same growing conditions as northern North Dakota.