Martin Zapalac was driving down Interstate 5 near Chehalis when he saw the bolt of lightning hit the motorcyclist in front of him in the pouring rain Thursday morning.

The man apparently was not seriously hurt. His condition wasn’t released, but Washington State Patrol Trooper Will Finn tweeted that he was “doing well.”

While it was a freak occurrence, the lightning and rain weren’t. Thunderstorms are expected to continue through Friday, bringing up to 2 inches of rain and possible flooding and mudslides.

The lightning hit the motorcyclist, a 59-year-old Tenino man, during the first heavy rain of the storm system, around 9:30 a.m. Thursday.

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He had zipped past Zapalac, 41, and his wife about a mile earlier, after Zapalac had slowed down on account of the deluge.

The Zapalacs, from nearby Winlock, Lewis County, felt reverberations in their Ford F-150, but when the motorcyclist slowed down and changed lanes to the right, they thought the lightning must have missed him. They slowed down and watched as he continued to move across the lanes, all the way onto the right shoulder.

There, he stopped, then collapsed sideways into the roadside barrier. Zapalac pulled over and the couple got out to check on the man.

At first the motorcyclist said he couldn’t hear what Zapalac was saying.

When the motorcyclist pulled off his helmet, the hair on the right side of his head was singed and his ear appeared blackened.

Zapalac said he looked dazed, asking, “Why am I stopped here?”

Other than the initial confusion, though, the man seemed coherent and unharmed, Zapalac said.

The motorcycle started, and the rider was able to drive it to the nearest exit, where the three waited for medics to arrive. He eventually was taken to Harborview Medical Center in Seattle with non-life-threatening injuries, according to Finn of the State Patrol.

Zapalac said he was surprised the man had been able to stay upright.

“I figured he would fly off the bike,” he said.

After a morning soaking that dropped more than a half-inch of rain in some Puget Sound spots in just a couple of hours, the rainfall slowed Thursday afternoon.

Brent Bower of the National Weather Service said heavy rains are likely to continue well into Friday.

That’s when the main storm system is expected to arrive.

So keep those slickers and umbrellas handy, because rainfall Friday could reach 2 inches in the Puget Sound lowlands, and as much as 4 inches in the Cascades.

A flood watch has been issued for Western Washington until 6 p.m. Friday.

Seattle-Tacoma International Airport, where Seattle’s official weather readings are taken, had just 2.65 inches of rain in the entire June-July-August period.

The rainiest Sept. 6 recorded there was four years ago, when 0.93 inches fell.

With all the rain, temperatures are expected to take a slight dip, and Friday is forecast to be in the upper 60s.

There’s good news, though: By Friday night, the risk of hazardous weather will drop, and the forecast calls for a mostly sunny weekend in the Puget Sound area, with highs Saturday and Sunday in the mid- to upper 70s.

Colin Campbell: 206-464-2033 or On Twitter, @cmcampbell6