Some tornadoes strike rapidly, without time for a tornado warning, and sometimes without a thunderstorm in the vicinity. When you are watching for rapidly emerging tornadoes, it is important to know that you cannot depend on seeing a funnel: clouds or rain may block your view.
The following weather signs may mean that a tornado is approaching:
- A dark or green-colored sky
- A large, dark, low-lying cloud
- Large hail
- A loud roar that sounds like a freight train
If you notice any of these weather conditions, take cover immediately, and keep tuned to local radio and TV stations or to a NOAA weather radioexternal icon.