It was a dark, humid morning in July, a day like any other for Evelyn Stern. Her husband had gone off to work and their two children had left for camp.

Enjoying a second cup of coffee, she was engrossed in a favorite journal when she heard, which sounded like a crash of glass.

Assuming that a window had been broken, she checked first-floor and basement windows for damage. There was none.

Next, she looked in the garage. The electronic door-opening device was hissing and spluttering. It had never done that before. Something was wrong.

She saw smoke coming from the second-floor master bedroom. She went up for a closer look and found a cracked wall, exposed and burning wires, scattered bits of plaster and bricks strewn across the lawn.

Only then did she suspect that the culprit was lightning. She raced over to a neighbor's house to call the fire department. . . .

What's the first thing you would have done in that situation?

According to Jim Campbell, an emergency warnings meteorologist with the National Weather Service in Silver Spring, Mrs. Stern did the right thing to call the fire department for help, but she should have left her house at the first sign of smoke. By going upstairs to investigate, she risked getting trapped.

Because the upstairs smoke detector had not gone off, Mrs. Stern said she had assumed the problem was minor.

Philip and Evelyn Stern of Flemington, N.J., were lucky. Their house did not go up in smoke and their insurance covered the damage, which consisted of the cracked wall, partially destroyed chimney, burnt out phone wiring and phone instruments. Also ruined were the switch on the water pump, the timing mechanism on the water softener, the electronic garage door-opening device, some electrical circuits and a bedroom light fixture.

The Stern family had never installed lightning rods on their house. Would this have spared them the worry? Yes, says meteorologist Campbell, provided they had been properly installed.

Statistics on file at the Lightning Protection Institute in Harvard, Ill., claim that 18,000 homes in this country are damaged each year.

Some areas of the country, according to Campbell, have more electrical storms than others. Residents of southern Florida contend with as many as 100 days of such storms each year. Much more fortunate are citizens of coastal towns in Washington state, Oregon and California, who experience 0 to 10 days of such storms. Washington, D.C., Milwaukee, San Antonio and the Sterns area score in at 30 to 40.

Exactly what is lightning?

Campbell describes it as "the product of thunderstorm electrification." Negative charges build up in the base of a thunderstorm and induce a positive charge on the ground. As the charges grow, the attraction becomes so great that they overcome insulating properties in the air. The lightning stroke is an electrical current flowing from the cloud to the ground. It is the current that is responsible for lightning damage and deaths.

Can you actually see the current of electricity?

Yes, says Campbell, "provided it is not obscured by rain or clouds."

Evelyn Stern remembers the sound associated with the actual impact of the electrical stroke as crashing glass, even though no glass was broken.

Says Cambell, the sound of impact would vary depending on what the lightning struck and the emotional state of those hearing it.

"You can measure your distance from the center of an electrical storm," he says, "by timing the delay between the lightning and the thunder. If there's a 10-second delay between the lightning and the thunder, the storm is two miles away. If there's a five-second delay, it's one mile away."

In the last 20 years, according to meteorologist Campbell, an average of 102 people per year have been reported killed by these bolts from the sky. Last year's number was 74. About two out of three lightning-caused deaths, he says, occur outside at the time of the storm.