Severe-weather alerts arrive in a confusing hierarchy of colors, words and push notifications, often while the sky is still blue. The wording is deliberate and the distinction between levels matters: it tells you whether to plan, prepare or act immediately. The terminology varies by country, but the underlying structure used in the United States and increasingly mirrored worldwide is easy to learn.
The watch vs. warning rule
- Watch: conditions are favorable for a hazard across a broad area over several hours. The ingredients exist; the trigger has not necessarily happened. Keep plans flexible, charge devices and know where shelter is.
- Warning: the hazard has been observed by radar, spotters or stations, or is imminent. This is the moment to act — move to shelter now, not after checking the window.
- Advisory: conditions are expected to be inconvenient or hazardous but not life-threatening if ordinary care is taken. Expect delays, slippery roads or difficult driving.
A memory aid that works: a watch means watch the sky and the alerts; a warning means move. People are hurt every year treating a tornado warning as if it were a watch, spending the precious minutes filming the storm instead of reaching shelter.
How alerts get their colors and names
National services such as the U.S. National Weather Service describe impacts in plain language and, in many countries, pair them with color tiers from advisory (yellow) through warning (orange/red) to extreme (violet). Tropical cyclones have their own naming and category systems based on sustained wind: tropical depression, tropical storm, then hurricane/typhoon/cyclone — the same phenomenon with different regional names — ranked from Category 1 to 5 by wind speed, though water usually kills more people than the wind does.
What each major hazard actually requires
Tornado
Move to a basement or an interior room on the lowest floor with no windows — a closet, bathroom or hallway. Cover your head with blankets or a helmet. Mobile homes and vehicles are unsafe even when tied down; leave them for a sturdy building or, as a desperate last resort, a low ditch. Highway overpasses are wind funnels and are dangerous; never shelter under one.
Severe thunderstorm and lightning
Inside a sturdy building or a fully closed metal-topped vehicle with windows up is safe; open shelters, porches, trees and water are not. Apply the 30-30 rule: go inside when the flash-to-bang gap is under 30 seconds, and remain inside until 30 minutes after the last thunder. Lightning can strike 16 km (10 mi) ahead of the rain.
Flood and flash flood
More than half of flood deaths involve vehicles. The rule is absolute: never drive through water on an unfamiliar road; as little as 30 cm (12 in) of moving water can float a car. 'Turn around, don't drown' is literal. Move valuables upstairs and leave low ground the moment a flash-flood warning is issued — minutes matter, and night-time warnings are the most dangerous.
Tropical cyclone, storm surge and hurricane
Evacuation orders are issued primarily for water: storm surge can arrive as a wall higher than a house, and freshwater flooding follows rain bands well inland. If told to leave, leave early with a full tank; sheltering in place beyond evacuation time is a leading cause of cyclone deaths. Board or tape is not a substitute; shutters or pre-fitted plywood protect windows, and interior rooms protect people.
Winter storm and extreme cold
Stay off roads during blizzard whiteouts and dress in layers covering all exposed skin in wind-chill emergencies. If trapped in a car, stay with it, run the engine briefly each hour only with the exhaust pipe clear of snow, and signal with a bright cloth. Indoors, never use generators, grills or camp stoves — carbon monoxide kills in minutes without smell.
Extreme heat and poor air quality
Heat is the deadliest routine weather hazard in many temperate countries. During heat warnings, move to air conditioning for parts of the day (cooling centres, libraries, malls), hydrate before thirst, and check on elderly neighbours. Air-quality alerts are weather warnings too: wildfire smoke and ozone demand reduced outdoor exertion and closed windows, especially for children and people with heart or lung conditions.
Before, during and after: a preparedness loop
- Before the season: know your home's safest room and local evacuation routes; keep water, non-perishable food, torch, radio, chargers and medication together.
- When a watch issues: charge phones, top up fuel and prescriptions, secure outdoor objects, and decide what would trigger leaving.
- When a warning issues: act on the specific guidance immediately — alerts now contain plain-language 'what to do' lines, so read them fully.
- After the event: avoid floodwater and downed power lines, check on neighbours, and document damage before cleanup where safe.
Forecasters are careful with the word 'warning'. Treating every warning as an instruction, rather than a suggestion, is the single biggest protection upgrade available.
Wherever in the world you are, enable your local official weather authority's free alerts, and keep one battery-powered or offline source for when networks fail. The hierarchy of watch, warning and advisory, combined with hazard-specific shelter knowledge, turns an alarming phone screen into a clear, calm sequence of actions.