Are there warning signs that indicate a tornado is approaching?

Question

Accepted Answer

Warning Signs of a Tornado Approach A dark, greenish sky is a classic sign of a tornado approaching. This is caused by the presence of large amounts of hail and heavy rain that block out sunlight and give the sky a greenish hue. If you notice a dark, greenish sky, take immediate shelter.
Visual Cues Low-lying clouds that appear to be rotating are another warning sign of a tornado. These clouds are called “tornado funnels” and are characterized by a rotating column of air that extends from the base of a thunderstorm to the ground. If you see a tornado funnel cloud, seek shelter immediately.
Audible Warning Signs A loud roar is another warning sign of a tornado. This is caused by the sound of the tornado’s winds rushing past objects in its path. The roar of a tornado can be heard from several miles away and is often compared to the sound of a freight train. If you hear a loud roar, take immediate action to seek shelter.
Preparing for a Tornado If you are in a vehicle, do not try to outrun a tornado. Instead, leave your vehicle and seek shelter in a nearby building or lie flat in a low-lying area, such as a ditch or depression, and cover your head with your hands. If you are in a building, go to an interior room or hallway on the lowest floor, away from windows and doors. Stay away from windows, doors, and exterior walls, and get under a sturdy table or desk and cover your head and neck with your arms.
Using a Tornado Siren If you hear a tornado siren, take immediate action to seek shelter. Tornado sirens are designed to alert people in the surrounding area of a tornado warning. If you hear a tornado siren, go to your emergency shelter or a nearby building and stay there until the danger has passed.
Staying Safe During a Tornado If you are caught outside during a tornado, try to find a nearby ditch or depression and lie flat, covering your head with your hands. Do not try to outrun a tornado or hide in a mobile home. If you are in a mobile home, leave immediately and go to a nearby building or shelter.