SAN FRANCISCO - Something strange is going on off the Northern California coast: The water is so warm that surfers don't need wetsuits, and fish rarely seen this far north are leaping in the waves.
The reason is El Nino, the cyclical flow of warm water from the equator. It's fun now, but experts warn the phenomenon might harm marine mammals and cold water fish like salmon, and bring torrential rain, flooding and mudslides to the area this winter.
That threat was the last thing on the minds of surfers like Jon Rider, who rode the waves in only a pair of long shorts.
"I haven't been able to do that in a long time," Rider said. Having grown up in Southern California, he said, "it reminded me of old times."
The normal bite of the cold ocean can leave a surfer in shivers after just a few minutes in the water, even with a wetsuit. And staying out too long can lead to hypothermia.
Waters that are normally as cold as 50 degrees this time of year are a relatively tepid 67, meaning the wave-riding can last for hours. And since past El Ninos have kept the waters warm for four to five months, it truly could be a surfer's endless summer.
"It's as warm as I've felt it," said bare-chested Mike Wirth, who happily trudged off the sand at Linda Mar Beach with board under arm. "Usually, there's a bite to it."
On the piers and fishing boats, anglers are hauling in mahi mahi, swordfish, marlin, sardines and other fish rarely seen in the cold waters off Northern California.
Farther north, off the Washington coast, two men landed an 104-pound marlin, the first such catch ever recorded in the area. On the Pacific Coast, marlin seldom stray north of the southern Baja peninsula.
"We realized what we had after it jumped six or eight times," said fisherman Mike Halbert. "We knew what marlin looked like. We were pretty shocked."
Off Dana Point in Southern California, an angler recently pulled in a tripletail - a fish that normally ranges from the southern Baja peninsula to Peru. It's only the second time the species has been seen in California waters since record-keeping began in the 1850s.
Even breathing is getting easier in California because of El Nino.
It has spawned a summertime pattern of low pressure, tropical moisture and lower temperatures, which have combined to help reduce Southern California smog, a byproduct of heat and stagnant air. Air quality officials said 1997 could prove to be the most smog-free year in the 40 years measurements have been taken.
"It's an incredibly exciting period," said Peter Pyle, a biologist at the Point Reyes Bird Observatory near San Francisco. "We think we're going to learn a lot from this."