Extreme Cold Warning in Michigan: what it means for snow, ice and the people clearing it

What replaced the Wind Chill Warning?

On October 1, 2024, the National Weather Service renamed its cold products nationwide. The NWS said the goal was to make clear that cold can be dangerous with or without wind, because people tended to tie the danger to wind alone.

What are the cold thresholds in Macomb County?

NWS Detroit/Pontiac uses these thresholds for Macomb County and the rest of southeast Michigan, from the national cold criteria referenced in NWS Instruction 10-515. They apply to the wind chill or the actual air temperature, whichever is the hazard.

Parts of the Upper Peninsula use colder thresholds. The NWS glossary puts the general threshold for dangerous wind chills at about -20°F and lower.

How fast can frostbite happen?

The NWS wind chill chart pairs air temperature and wind speed with how long exposed skin takes to freeze. A few values from it:

The CDC lists the nose, ears, cheeks, chin, fingers and toes as the usual frostbite sites. Warning signs are numbness and skin that turns white or grayish-yellow, or feels unusually firm or waxy. If you suspect frostbite, get indoors, warm the area with warm (not hot) water or body heat, do not rub it, and get medical care. Shivering, confusion, fumbling hands, slurred speech or drowsiness can mean hypothermia, which needs medical attention right away, according to the CDC.

What does deep cold do to snow and ice work?

• Rock salt stalls. It slows badly below about 20°F and effectively stops below about 15°F, and advisory-level wind chills come with air around 10°F or colder. The choices are calcium chloride, sand for traction, or waiting. The chemistry is in does salt work in cold weather.
• Packed snow stays packed. Snow that is driven or walked on before it is cleared presses into an icy layer that nothing will soften at these temperatures. Clear it before it packs.
• Afternoon melt refreezes. Sun on dark pavement can melt the edge of a snow pile even on a cold day. The water freezes again the moment the sun drops, which is how black ice forms.

How do you shovel safely in extreme cold?

• Go out in short sessions and warm up inside between them. The CDC advises limiting time outdoors in extreme cold.
• Cover every bit of skin: a hat, a scarf or knit mask over the face, mittens or gloves, and several loose, water-resistant layers.
• Change out of wet gloves and clothing as soon as you can. Wet layers lose much of their insulation.
• Push, do not lift, and take small loads. Cold air raises blood pressure while shoveling raises the heart rate. If you have heart disease or its risk factors, the American Heart Association advises not shoveling at all; see shoveling and your heart and how to shovel without hurting your back.

What about vents and pets?

Drifting snow can bury the furnace and water heater vents on the side of a house, and a blocked vent can let carbon monoxide build up inside. Check those vents after every storm and every windy day. Our after-the-storm checklist covers the rest.

For dogs, use less de-icer, not more. Below about 15°F rock salt is not melting anything anyway, and every extra handful is something for paws to pick up. Wipe paws after walks; pet-safe ice melt explains what the labels mean.