From tornado watches to flash flood emergencies — know the difference between alert types, understand risk levels, and learn what actions to take when severe weather threatens.
A watch means weather conditions are favorable for severe weather to develop. Meteorologists have identified atmospheric ingredients — instability, wind shear, moisture — that could combine to produce severe storms.
This is your time to prepare. Know where your shelter is, charge your phone, and stay tuned to the weather.
A warning means a trained spotter has spotted the hazard, or radar has indicated it. The threat is imminent or happening right now in the warned area.
This is your time to act immediately. Seek shelter, follow your safety plan, and do not wait.
Emergency Alert vs. Advisory: There's also a third tier — the Advisory — issued for less significant hazards that may cause inconvenience but are not life-threatening. Always check for warnings first when severe weather is possible.
Broken branches, shallow-rooted trees uprooted. Chimneys and gutters damaged. Little structural damage.
Roofs peeled off well-constructed homes. Mobile homes overturned. Windows broken.
Well-built homes badly damaged. Large trees snapped. Boxcars overturned. Light-object missiles generated.
Well-built homes completely destroyed. Heavy cars lifted and thrown. Trees debarked.
Well-built homes leveled. High-rise buildings significantly damaged. Cars thrown considerable distance.
Incredible structural damage. Strong frame houses leveled and swept away. Steel-reinforced concrete structures badly damaged.
Severe threshold: The NWS considers hail ¾ inch (penny-size) or larger as severe. Baseball-sized hail (>2.75″) can penetrate car roofs and cause severe injuries. Never stand outside during hail storms.
Unlike tornadoes, straight-line winds blow in one direction and can affect a broad area. Downbursts and microbursts from thunderstorms can produce winds exceeding 100 mph — strong enough to damage roofs, snap trees, and flip vehicles.
Move away from windows and doors. Avoid sheltering under trees. If outdoors, lie flat in a low-lying area. Mobile homes offer little protection — seek a sturdy building. Flying debris is the primary cause of injuries.
Derecho: A widespread, long-lived windstorm associated with a band of rapidly moving showers or thunderstorms. Derechos can cause hurricane-force winds over hundreds of miles and are often underestimated.
Never attempt to drive through flooded roadways. Just 12 inches of rushing water can carry away a small vehicle. Half of all flash flood deaths occur in vehicles.
Flash floods can occur miles from the rainfall. If you're in a canyon, low-lying area, or near a stream, be aware that water can rise rapidly with little warning.