Violent thunderstorms with strobelike lightning and drenching rains touched off numerous fires yesterday, bedeviled commuters, and might have contributed to the deaths of two men.

Two kayakers drowned during an afternoon outing on the Brandywine Creek, which had been swollen by downpours during a spectacular round of thunderstorms during the morning.

Almost 2,000 lightning strikes were detected in the immediate Philadelphia area between 6 and 9 a.m., said Lee Robertson, meteorologist with the National Weather Service in Mount Holly.

A second round of drenching storms formed during the afternoon, causing some flooding in parts of western Chester County. However, they were not as damaging or as widespread.

Peco Energy said the morning storms caused about 10,000 power outages, scattered throughout its coverage area.

And lightning-ignited fires broke out all over the place, including Philadelphia; Chester Springs, Chester County; Stafford Township, Ocean County; and Rehoboth Beach, Del.

A lightning bolt can heat the surrounding air to up to 18,000 degrees Fahrenheit - significantly hotter than the surface of the sun, said Richard J. Blakelee, senior researcher and lightning expert at NASA's Marshall Space Flight Center in Huntsville, Ala.

One bolt set a barn on fire in Bedminster, and another forced the evacuation of an apartment building in West Philadelphia after blowing off part of the facade and sparking a small blaze.

As the storms rolled through, the thunderstorms turned day into night, snarled traffic, and drenched pedestrians.

The light show spoke to the intensity of the storms, said Blakeslee: The more lightning, the stronger the storms. For reasons that aren't entirely clear, he added, some storms produce more cloud-to-ground lightning than others, and the morning storms appeared to fit that profile. Typically, only about 25 percent of all bolts ever reach the ground; the rest travel from cloud to cloud.

The fireworks were the visible evidence that the region was caught in the cross fire of an air-mass battleground, with a cool front trying to move eastward and a warm front nudging northward.

An inch of rain was measured in a mere 20 minutes in Drexel Hill during the morning. Some flooding was reported in the West Chester area, and standing water covered parts of the Schuylkill Expressway.

In Downingtown, close to two inches of rain was reported, punctuated with dime-size hail.

Some of the rain evidently engorged the Brandywine Creek. Shortly after 1:40 p.m., emergency workers were called to the Brandywine in East Bradford Township, near the Brandywine Picnic Park, at Creek Road and Route 52.

Students from Radnor Middle School who were at the park for a picnic witnessed two kayaks capsizing and, as they were boarding buses, watched rescue workers battling the rough waters, school officials said. In a note to parents, the officials said that the kayakers were not connected with the school and that all the children were safe.

Police said an unidentified man was pulled from the swift-moving water and was taken to Chester County Hospital, where he died.

Late last night, divers continued their search for his companion, who was presumed dead.

Both men remained unidentified last night.

West Chester Police Chief Scott L. Bohn said employees from Brandywine Picnic Park observed the two men, both of whom appeared to be wearing life jackets, going over a 4-foot dam on the creek. When the men failed to surface, the employees called 911, he said.

Bohn said the dive crews were hampered by the rising waters and undercurrents, factors that may have played a role in the accident. In a briefing to reporters about 10 p.m., the chief said the crews would carry on as long as weather permitted.

For all the rain, most of the reported flooding yesterday was minor. Stream levels still are recovering from what was generally a bone-dry winter.

But don't be surprised if flood threats pop up during the next few days. More showers are possible today, tomorrow, and Friday.