Tornado Safety: Where to Shelter & What the EF Scale Means

The United States averages more than 1,000 tornadoes a year, more than any other country. Most are brief and weak, but a strong tornado can destroy well-built homes, and the time between a warning and a tornado's arrival is often only ten to fifteen minutes. Tornado safety comes down to two things decided long before the sky turns green: how you'll find out about a warning, and exactly where you'll go when you do.

Getting the warning

A Tornado Warning means a tornado has been seen or is strongly indicated by radar (see NWS Watches vs. Warnings Explained). The warning only helps if it reaches you, and no single alert method is reliable on its own:

• Wireless Emergency Alerts on your phone are automatic for Tornado Warnings. Check that emergency alerts are turned on in your phone's settings.
• NOAA Weather Radio with a battery backup will sound an alarm for warnings in your county, even overnight and during a power outage.
• Outdoor sirens are designed to warn people outdoors. Many people can't hear them inside, especially in a storm, with the air conditioning running, or asleep. Never rely on sirens alone.
• Apps and TV, including RadarBug's NWS alert layer, add awareness but depend on your phone being on, charged, and not on silent.

Tornadoes at night are more than twice as likely to be deadly as daytime tornadoes, largely because people are asleep and the tornado can't be seen. When a Tornado Watch is in effect overnight, make sure at least one alert method can wake you.

Where to shelter

The goal is to put as many walls and floors between you and the outside as possible, get as low as you can, and protect your head. Flying debris causes most tornado injuries and deaths.

Wear sturdy shoes and, if you have one, a helmet (bike, sports, or construction). Head injuries are a leading cause of tornado deaths, and shoes matter for walking out through broken glass and debris afterward. Keeping both in or near your shelter spot saves precious seconds.

Safe rooms and storm shelters

A FEMA-standard safe room, either built into a home or installed as an in-ground or above-ground shelter, is designed to withstand the strongest tornadoes. If you live in a tornado-prone area without a basement, or in a mobile home community, a safe room or community shelter is worth serious consideration. Many states and counties offer rebates for residential safe rooms. If you rely on a community shelter, find out in advance whether it opens automatically when a watch or a warning is issued, and how long it takes you to get there.

Tornado myths that cost lives

• Myth: Open windows to equalize pressure. This does nothing to protect a house and wastes time you should spend getting to shelter. Windows will break anyway in a direct hit; stay away from them.
• Myth: Highway overpasses are good shelter. Overpasses can act as wind tunnels that accelerate wind and debris, and people stopped under them block roads others need for escape. People have been killed sheltering under overpasses.
• Myth: The southwest corner of the basement is safest. No corner is reliably safest; debris direction depends on the tornado's path. What matters is getting under something sturdy and away from heavy objects on the floor above.
• Myth: Tornadoes don't hit cities, rivers, or mountains. Tornadoes have struck downtown areas, crossed major rivers, and climbed mountain ridges. Geography offers no protection.
• Myth: You'll always see or hear it coming. Many tornadoes are hidden by rain ("rain-wrapped") or darkness. The often-described freight-train roar may only be audible moments before impact. Act on the warning, not on what you see.

How tornadoes are rated: the Enhanced Fujita scale

Wind speeds inside a tornado are almost never measured directly. Instead, after a tornado, National Weather Service survey teams examine the damage and estimate the winds that would have caused it, based on how well different structures (from barns to brick homes to trees) resist wind. That estimate sets the tornado's rating on the Enhanced Fujita (EF) scale:

Because ratings are based on damage, a violent tornado that crosses only open fields may be rated lower than its true winds, since there was little for it to damage. About three quarters of U.S. tornadoes are rated EF0 or EF1, but the rare EF3 to EF5 tornadoes cause the large majority of deaths. Ratings are assigned after the fact, often a day or more later, and warnings don't predict them. Treat every Tornado Warning as potentially violent.

After the tornado

• Stay in shelter until the warning expires or you're sure the threat has passed; more than one tornado can come from the same storm.
• Watch for downed power lines, broken gas lines (leave immediately if you smell gas), and unstable structures.
• Use a flashlight rather than candles, and never run a generator indoors or in a garage.
• Wear sturdy shoes, long sleeves, and gloves when moving through debris.
• Text rather than call, to keep phone networks free for emergency calls.

What to watch on RadarBug

• Keep NWS Alerts & Warnings on whenever a Tornado Watch covers your area. Tornado Warnings are drawn as red polygons along the storm's expected path.
• In the radar loop, watch for a hook-shaped appendage on the storm's trailing side, described in How to Read a Weather Radar. Tornadoes can also form along squall lines without an obvious hook.
• Set a home location so you can quickly see whether a warning polygon includes your house when you're away from home.