Lightning strikes the United States about 25 million times a year.

Lightning kills 20 or more people in the U.S. each year, and hundreds more are severely injured, according to the National Weather Service.

Here are some tips that will help you stay safe during a thunderstorm:

1. No place outside is safe when thunderstorms are in the area.

2. If you hear thunder, lightning is close enough to strike you.

3. When you hear thunder, immediately move to a safe shelter - a substantial building with electricity or plumbing or an enclosed, metal-topped vehicle with windows up.

4. Stay in a safe shelter at least 30 minutes after you hear the last sound of thunder.

Working outdoors? Here are lightning safety tips when working outdoors from OSHA.

5. Stay off corded phones, computers and other electrical equipment that put you in direct contact with electricity.

6. Avoid plumbing, including sinks, baths and faucets.

7. Stay away from windows and doors, and stay off porches.

8. Do not lie on concrete floors, and do not lean against concrete walls.

If you are caught outside with no safe shelter anywhere nearby, the following actions may reduce your risk:

9. Immediately get off elevated areas such as hills, mountain ridges or peaks.

10. Never lie flat on the ground.

11. Never shelter under an isolated tree.

12. Never use a cliff or rocky overhang for shelter.

13. Immediately get out and away from ponds, lakes and other bodies of water.

14. Stay away from objects that conduct electricity (barbed wire fences, power lines, windmills, etc.)

MORE: Here are five ways lightning strikes people.

Lightning may cause many injuries, including heart attacks, burns, shock, and sometimes blunt trauma. Treat each of these injuries with basic first aid until help arrives. Do not move victims who are bleeding or appear to have broken bones.

15. When someone is struck by lightning, get emergency medical help as soon as possible. If more than one person is struck by lightning, treat those who are unconscious first.

16. Safety is a priority. Be aware of the continuing lightning danger to both the victim and rescuer. If the area where the victim is located is high risk, the victim and rescuer could both be in danger. If necessary, move the victim to a safer location.

17. Lightning often causes a heart attack. Check to see if the victim is breathing and has a heartbeat.

18. If the victim is not breathing, immediately begin mouth-to-mouth resuscitation. If the victim does not have a pulse, start cardiac compressions as well (CPR). Continue resuscitation efforts until help arrives. If the area is cold and wet, putting a protective layer between the victim and the ground may help decrease hypothermia (abnormally low body temperature). What is hands-only CPR and how to perform it - click here to learn more.

19. Each year, more deaths occur due to flooding than from any other thunderstorm related hazard. The Centers for Disease Control and Prevention reports that over half of all flood-related drownings occur when a vehicle is driven into hazardous floodwater. The next highest percentage of flood-related deaths is due to walking into or near floodwaters. It is never safe to drive or walk into floodwaters. CLICK HERE for 6 flooding safety tips to follow.

Source: National Weather Service | Centers for Disease Control and Prevention