District Issues Protective Actions for Thunderstorms Thunderstorms can bring heavy rains (which can cause flash flooding), strong winds, hail, lightning and tornadoes. It is possible for a thunderstorm to affect one location in the course of a few hours, which can cause downed trees, downed power lines, power outages and massive amount of debris on roads.  In general, you should know the difference between a watch and a warning.  A severe thunderstorm WATCH means that a severe thunderstorm (damaging winds 58 miles per hour or more, or hail three-fourths of an inch in diameter or greater) is likely to develop. A severe thunderstorm WARNING means that a severe thunderstorm has been sighted or indicated by weather radar. In the event of a Watch or Warning you should: Go to a safe place, turn on a battery-operated radio or television and wait for the "all clear" by the authorities. Secure outdoor objects such as lawn furniture that could blow away or cause damage or injury and take light objects inside (if weather permits). Shutter windows securely and brace outside doors. Turn off all electrical equipment, including telephones and televisions.  Avoid bathtubs, water faucets and sinks because metal pipes can transmit electricity. If outdoors: Go inside a building or car. If no structure is available, find an open space and squat low to the ground as quickly as possible. Avoid tall structures such as towers, tall trees, fences, telephone lines or power lines. Stay away from natural lightning rods such as golf clubs, fishing rods or bicycles. Stay from bodies of water and flood prone areas. After the storm, DO NOT attempt to move downed power lines, trees or other fallen objects. If in a car: Pull safely onto the shoulder of the road away from any trees that could fall on the vehicle. Stay in the car and turn on the emergency flashers until the heavy rains subside. Do not attempt to drive over a flooded road - you could be trapped or stranded. The depth of the water is not always obvious, or the road could be washed away. If you can't see it, you can't be sure it's there.