Safety & Alerts
Weather safety terminology — from advisories to wind chill warnings. The alerts and terms that keep you safe in winter weather.
Advisory
A National Weather Service alert issued for weather conditions that are inconvenient but not severe enough to warrant a warning. Common examples include winter weather advisories and wind advisories.
Black Ice
A thin, transparent layer of ice that forms on roads and sidewalks, usually when temperatures hover near freezing and moisture refreezes. It is nearly invisible against dark pavement, making it one of the most dangerous winter driving hazards.
Cold Urticaria
A real medical allergy to cold air or cold water in which exposure triggers histamine release, causing hives, swelling, and in rare cases anaphylaxis. Severe cases can react to holding an iced drink or jumping into cold water.
Danger Zone (Food Safety)
The temperature range between 40°F and 140°F in which bacteria multiply rapidly. Critical for hunters: a deer carcass left to hang in 50°F weather is in the Danger Zone and should be cooled mechanically.
Frostbite
Tissue damage caused when skin and underlying tissues freeze, most commonly affecting fingers, toes, ears, and nose. Wind chill can cause frostbite in under 30 minutes at extreme cold temperatures.
Hypothermia
A medical emergency in which the body's core temperature drops below 95°F. Wet clothing, especially cotton, dramatically accelerates heat loss and is the leading contributor to hypothermia in mild cold conditions.
Ice Dam
A wall of ice that forms at the edge of a roof when melted snow refreezes in the gutters. Ice dams trap melting water under shingles, where it can leak through ceilings and rot the roof deck.
Visibility
The distance at which an object can be clearly seen. Snowstorms and fog can drop visibility to near zero, which is the legal trigger for many winter driving advisories and school closures.
Winter Storm Warning
A National Weather Service alert issued when severe winter weather is occurring, imminent, or highly likely. Warnings are more serious than watches and indicate that travel will become dangerous.
Winter Storm Watch
A National Weather Service alert issued when severe winter weather is possible within 48 hours. A watch means conditions are favorable; a warning means it is happening.