During lightning storms, stay inside, away from windows, and don't use the telephone. Twisters' are powerful rotating winds. Most often they grow out of thunderstorms. When warm, moist air collides with cool, dry air, a huge updraft can result, creating a tornado. The funnel-shaped trunk that drops down from a thundercloud may whirl at a deadly 300 mph, destroying everything in its path.
Scientists know when conditions are ripe for tornadoes to form.
However, even with top technology, forecasters can predict only about 20 minutes ahead of time where a tornado is likely to hit. During a tornado warning, try to stay indoors under a stairway, mattress, or heavy furniture. Ice crystals tossed around in clouds by updrafts can form hailstones. As the crystals pick up more moisture, these ice balls grow. If they become so heavy the air currents can't hold them up, hail will fall.