How cold is it in the northern U.S.? in Minneapolis, a high Monday of -2°F marked the first time in 4 years the city recorded a subzero high. Near Duluth, Minn., the town of (no fooling) Embarrass hit -36°F.

Chilling. A few thoughts:

1. Beware frostbite—dull, waxy skin that feels numb or tingly. Among the tips presented in a 2011 REI Blog post by John Hovey, an instructor with the Wilderness Medicine Institute of the National Outdoor Leadership School (NOLS):

• Got badly chilled fingers? Use armpits, yours or a friend’s, as an initial reheating stash spot if no other options are available.
  
  
• Iced-over toes? In an emergency, plant them on a willing companion’s belly—because the gut is central to the body’s heat-generating core. (Note: Anyone who would volunteer their tummy for such service is a most noble human.)

2. Icy conditions can turn Farmville into Adventuretown. Example: Ice climbing in the Midwest, on ice-coated silos.

Making vertical ascents on frosted silos is the happening thing in Cedar Rapids, Iowa. (Wednesday’s forecast high: 16°F.). Here University of Northern Iowa students climb for class credit, and kids as young as 10 climb just for fun. CNN reports:

3. Ice becomes a spectacle. Frozen spray from the upper tier of 2,425-foot Yosemite Falls in Yosemite National Park sometimes breaks loose on sunny days and makes an impact. Boom goes the waterfall: