TORNADOES
Tornadoes are nature’s most violent storms. Spawned from powerful thunderstorms, tornadoes can cause fatalities and devastate a neighborhood in seconds. A tornado appears as a rotating, funnel-shaped cloud that extends from a thunderstorm to the ground with whirling winds that can reach 300 miles per hour. Damage paths can be in excess of one mile wide and 50 miles long. Every state is at some risk from this hazard. Some tornadoes are clearly visible, while rain or nearby low-hanging clouds obscure others. Occasionally, tornadoes develop so rapidly that little, if any, advance warning is possible. Before a tornado hits, the wind may die down and the air may become very still. A cloud of debris can mark the location of a tornado even if a funnel is not visible. Tornadoes generally occur near the trailing edge of a thunderstorm. It is not uncommon to see clear, sunlit skies behind a tornado.

QUICK FACTS ABOUT TORNADOES
They may strike quickly, with little or no warning.
They may appear nearly transparent until dust and debris are picked up or a cloud forms in the funnel.

They can become wrapped in rain and hard to see.
The average tornado moves Southwest to Northeast, but tornadoes have been known to move in any direction.
The average forward speed of a tornado is 30 mph, but may vary from stationary to 70 mph.
Tornadoes can accompany tropical storms and hurricanes as they move onto land.
Waterspouts are tornadoes that form over water.
Tornadoes are most frequently reported east of the Rocky Mountains during spring and summer months.
Peak tornado season in the southern states is March through May; in the northern states, it is late spring through early summer.
Tornadoes are most likely to occur between 3 pm and 9 pm, but can occur at any time.

WARNING SIGNS TO LOOK FOR: 
Dark, often greenish sky
Large hail
A large, dark, low-lying cloud (particularly if rotating)
Loud roar, similar to a freight train.
If you see approaching storms or any of the danger signs, be prepared to take shelter immediately.

WHAT TO DO BEFORE A TORNADO:
Make sure you have prepared supplies for at least three days, I.e. Your bug out bag. I personally would store your bugout bag in your storm shelter if you have one or the equivalent supplies. 
Make sure you have a family communication plan in case you are separated. See the article on that for how to make one.
Know where you are going to take shelter in the event of a tornado. Practice going to your safe place and know how to get there quickly. 
Know how and where to turn things off such as electrical, natural gas, and propane. 

WHERE TO SEEK SHELTER IN A CONVENTIAL BUILDING:
Go to a pre-designated area such as a safe room, basement, storm cellar, or the lowest building level. If there is no basement, go to the center of a small interior room on the lowest level (closet, interior hallway) away from corners, windows, doors, and outside walls. Put as many walls as possible between you and the outside. Get under a sturdy table and use your arms to protect your head and neck.
In a high-rise building, go to a small interior room or hallway on the lowest floor possible
.

WHAT TO DO IN A MANUFACTURERED HOME, MOBILE HOME, OR PORTABLE BUILDING:
Get out immediately and go to a pre-identified location such as the lowest floor of a sturdy, nearby building or a storm shelter. Mobile homes, even if tied down, offer little protection from tornadoes.

IF CAUGHT OUTSIDE AND NOT NEAR A STURDY STRUCTURE:
If you are not in a sturdy building, there is no single recommendation for what last-resort action to take because many factors can affect your decision.

POSSIBLE ACTIONS TO TAKE:
Immediately get into a vehicle, buckle your seat belt and try to drive to the closest sturdy shelter. If your vehicle is hit by flying debris while you are driving, pull over and park.
Take cover in a stationary vehicle. Put the seat belt on and cover your head with your arms and a blanket, coat or other cushion if possible.
Lie in an area noticeably lower than the level of the roadway and cover your head with your arms and a blanket, coat or other cushion if possible.
In all situations:
Do not get under an overpass or bridge. You are safer in a low, flat location.
Never try to outrun a tornado in urban or congested areas in a car or truck. Instead, leave the vehicle immediately for safe shelter.
Watch out for flying debris. Flying debris from tornadoes causes most fatalities and injuries.

WHAT TO DO AFTER THE TORNADO PASSES: 
Watch out for debris, if unable to get out wait for help. Do NOT try to move debris unless absolutely necessary.
Assess and treat any medical injuries if able. See the articles on the medical section. 
Watch out for hazards such as debris, broken glass, downed electrical lines, and leaking gas. 
Activate your family's emergency communcation plan of separated. 
Looting is a big problem after any natural disaster. Prepare accordingly. 
If your residence is severely damaged, be prepared to evacuate.