Winter storm watch vs. warning vs. advisory, and cold alerts

Winter alerts come in three steps: a watch means plan, an advisory means slow down, and a warning means change your plans. What it takes to reach each step depends on where you live, so the same few inches can bring a warning in one city and nothing in another.

Three steps, three different asks

• Winter Storm Watch: a significant winter storm is possible, often 12 to 48 hours ahead. Plan now, and check back.
• Winter Weather Advisory: snow or ice below warning level, but roads can still be slick. Slow down and allow extra time. "Advisory" doesn't mean harmless.
• Winter Storm Warning: a significant storm is coming or under way. Delay travel. If you must go, take a full tank, warm layers, an emergency kit and a charged phone.

The watch vs. warning guide covers the same idea for every hazard.

Why 2 inches can be a warning and 6 inches isn't

Each National Weather Service office sets its own thresholds, based on what its area is ready for. A Winter Storm Warning might take about 6 inches of snow in Minneapolis and about 2 in Atlanta, where there are fewer plows and drivers see snow less often. Judge an alert by its name, not by comparing snow totals with somewhere else.

Blizzards are about wind, not snow

A Blizzard Warning isn't about how much snow falls. It means frequent wind gusts of 35 mph or more with falling or blowing snow cutting visibility below a quarter mile, for three hours or more. A blizzard can happen with little new snow, when strong wind lifts what's already on the ground. Whiteouts make travel dangerous to impossible. Stay off the roads. If stranded, stay in your vehicle.

An Ice Storm Warning usually means around a quarter inch of ice or more. The freezing rain guide explains why ice is the dangerous one.

The new cold alert names

The National Weather Service has renamed its cold alerts. If you remember wind chill warnings, these are what replaced them:

• Extreme Cold Watch (was Wind Chill Watch): dangerous cold is possible. Plan now: check heat, pipes, pets and neighbors.
• Cold Weather Advisory (was Wind Chill Advisory): cold enough to hurt with long exposure. Dress in layers and cover exposed skin.
• Extreme Cold Warning (was Wind Chill Warning): frostbite can happen quickly. Limit time outside, cover skin, bring pets in and check on neighbors.

The new alerts are about dangerous cold, with or without wind: a still, bitterly cold night can bring one too.

Wind chill: what the wind does to your skin

Wind chill is how cold it feels on bare skin, because wind carries body heat away faster. At 0°F with a 15 mph wind, the wind chill is −19°F, and exposed skin can freeze in about 30 minutes. The colder the wind chill, the faster it happens. Wind chill doesn't make your car or your pipes colder than the air: they only cool to the actual temperature. It's about people and animals.

Getting winter alerts from Atmostorm

Get warnings emails you winter warnings for your place, with no account, whenever the NWS rates them severe or worse, as it does nearly all of them. On your phone, you get them if you also tick the box for winter storm and other warnings. Watches and advisories aren't sent; you'll find them on the map and your town's page.

Watch the short explainer on our YouTube channel.