The best advice? Simply avoid them.
And, no matter what, don't become electricity's "path to ground," warned Mike Glowacki of Public Service Electric and Gas, or PSE&G, New Jersey's largest power company.
He told The Early Show consumer correspondent Susan Koeppen Thursday that the first thing you should do is be aware of power lines overhead.
"The lines are up there, and you don't realize they're up there," he explained. "After a while, it's like being in the driveway: Your car's just there. You know it's there. The wires, you don't realize they're there.
"When you're doing work around your house, such as cleaning gutters, washing windows, or painting, and you take a ladder out, stick it up in the air, on the side of the house, that's when you realize they're there.
"If you lose control of a ladder, let the ladder go. If you hold on to the ladder, you will become the path to ground. And that's what you do not wanna be, the path to ground."
A colleague of Glowacki's demonstrated what could happen if you do become the path to ground. He held a ladder up to a 7,600-volt power line. A blue arc of electricity seemed to pop out of the ladder.
"That's electricity making the path to the ground," Glowacki explained. "You do not want to become the path to ground. That will shock you, hurt you, do some damage to you."
Another potential danger: kids playing with balloons or kites or other devices that can go up in the air.
Again, a Glowacki co-worker showed what could happen, letting a Mylar
balloon float into a power line. It caught fire immediately.
"If you have a rope to (the balloon) or a string on it, you'll become the path to ground with that," Glowacki emphasized. "Again, you do not want to become the path to ground. You want to watch where you put those things. Be aware of the lines above you."
"A live line," Glowacki says, "could be sitting on the ground, spitting, sparking or making any kind of noise. It could also be lying there without making any noise at all. Lying there live. And you wouldn't know it.
"If it's in your way, and you try to grab it to move it out of the way, you're gonna injure yourself. You're gonna again become that path to ground, and that's what you do not want. Don't touch it. Call your utility. Call the police. They'll get in touch with us and we'll get out there as soon as we can and take care of it for you."
What happens if you are in a car during a storm and power lines come down, trapping you in the car with a power line on top?
"Stay in the car," Glowacki said flatly. "That the best thing, that's the safest thing can you do, just stay in your car. Again, the police department will be out there, and get in touch with the utility company. The utility company can come out and take it off the car.
"Stay in the car. You do not want to jump out of the car. You may become that path to ground and you do not want that. Stay in the car."
Also, avoid the natural tendency to try to help someone being shocked.
"Stay away. Do not grab them," Glowacki cautions. "It becomes a chain reaction. They're the path to ground, next thing ya know, you'll become the path to ground by touching them. It will come in through you. Again, call the police, call the utility company. Get somebody else there that's qualified and they'll take care of it for you. Call 911, and stay put.
"If you run to help that person, you'll be the second person in trouble. And then it could cascade."
In addition, the ground around a downed power line can become energized, meaning, dangerous. Another good reason to steer clear, Glowacki says.