The benefits of extreme cold in Minnesota

My dad used to say our cold Minnesota winters “keep out the riffraff.”

That wouldn’t win him any PC awards these days. But it’s true in the bigger context I now understand to include critters like invasive insect species that can harm Minnesota’s forests.

Emerald Ash Borer. Image: David Cappaert, Michigan State University

Minnesota’s extreme cold has benefits. My conversations with renowned University of Minnesota Center for Forest Ecology director Lee Frelich have taught me that extreme cold in Minnesota is critical to forest health.

Lee says extreme cold is critical for achieving high insect mortality rates. The cold is good news for ash trees who are under attack from the emerald ash borer.

Fig. 1. Location of United States and Canada weather stations used in this study,and ranges of green,white,and black ash in North America according to Little (1971). R.D. DeSantisetal./Agricultural and Forest Meteorology 178–179(2013)120–128

When temperatures hit minus 36 to minus 40 in Minnesota, up to 99 percent of ash borer larvae can die.

Coldest temperatures recorded in largest and smallest diameter logs used in larval COLD HARDINESS OF EMERALD ASH BORER, AGRILUS PLANIPENNIS: A NEW PERSPECTIVE Robert C. Venette1 & Mark Abrahamson2

Extreme cold in Minnesota keeps away other invasive pests too. But climate change in Minnesota is making temperatures like minus 40 up north and minus 20 in the Twin Cities less frequent.

Image via Minnesota Rose Gardener.

So when you see extreme cold in the forecast, there are reasons for Minnesotans to celebrate.


  • Interesting.
    Is there snow coming on Friday? Please say “yes.”

    • JonasGrumby

      Yes. Just not here.

  • Rob

    Meh. I’ve yet to see the value of winter in general, let alone hideously cold ones. Another way to minimize ash borer damage is for municipalities not to plant only ash trees when doing new or replacement plantings. St.Paul’s urban forest is becoming ever more denuded because of this monoculture mindset. You’d think the Elm Disease debacle would’ve been enough to show the stupidity of single-species planting, but clearly not.

    • Skeptic68

      Just goes to show how much you don’t know about winter.

  • jon

    I was curious about your graph there and if 2016-2018 would make any difference on it…
    Found the data here:

    and charted it out quick in excel… figured I’d share incase any one else was curious…

  • Guest

    A cure for bedbugs or roaches is to pour RV antifreeze (OK to drink) down traps and toilets, throw open the doors and windows on the coldest weekend and get a motel. Maybe stand mattress upright to allow cold to circulate around it.

    Come back, turn up furnace slowly (to allow wood to adjust) then bugs and larvae inside are dead.

    Way more friendly than burning a sulfur candle to create poison gas as was done back in the lumberjack days.

    • I’m not so sure that would work. There is a lot of thermal latency in a house and I think there are plenty of spaces that would not get cold enough to accomplish the task.

      • Guest

        30 below and make it a long weekend, still cheaper than the hassle of bugs being spot treated.