Whale-watching along most parts of the Pacific coast requires long, wintry forays through cold mists and choppy seas. But if you want to stand on the beach and watch frolicking orcas in the warm flush of summer and fall, go to where the whales make their summer homes, along the mountain-rimmed archipelago that straddles the western border between the United States and Canada.

Of the three islands between Vancouver Island and mainland Washington that are big enough to host towns—San Juan, Orcas, and Lopez—San Juan is the center of action, both human and cetacean. Within its 55 square miles, this westernmost isle boasts the largest town in the San Juans (the village of Friday Harbor, with its 2,045 citizens) as well as tidy farms, forest-rimmed meadows, and fishable lakes. Most important, of course, to the resident orcas that ply the deep waters of the Haro Strait are the five kinds of salmon coursing through the channel; one killer whale can wolf down more than 200 pounds of fish every day.

Each May, three distinct clans, or pods, of these fish eaters follow spawning salmon to within nibbling distance of the San Juan shore, lingering to feast through September or beyond. The island offers scientists as well as tourists an unrivaled perch for making the sort of repeated observations crucial to understanding whale behavior. Among recent lessons learned: San Juan's three resident pods, led by 80- or 90-year-old grannies, are matrilineal clans, each with its own dialect of squawks and squeals. Young orcas venture beyond the clan briefly to mate, but otherwise swim with Mom for life. And though San Juan's resident pods are strictly fish eaters, that's not true of all killer whales. Stealthy clusters of orcas known as transients periodically pass through the same waters to hunt seals, sea lions, and other whales. Scientists note that although the transients and residents have overlapping territories, they don't mix.

Not so human residents and visitors to the island. San Juan is peppered with artistic entrepreneurs from the mainland who came for the weekend and stayed, patching together odd jobs to survive in an isolated island economy. The result is an inventive delight for tourists: One day, after an hour's fragrant wandering through the fields of the Pelindaba Lavender Farm, I headed into town to a lunch spot that's hard to find, but well worth the trouble. At the back of a local nursery, hidden amid the tree ferns and begonias, the Backdoor Kitchen serves a multiethnic menu. Tuck into your stir-fry near a stand of bamboo or swaying ficus and you may wonder why every nursery doesn't have a café, and every café a nursery.

San Juan has many more treasures. Explore, for example, windswept American Camp at San Juan Island National Historic Park to learn how a hungry pig nearly triggered a war 150 years ago, or visit Roche Harbor, the resort whose historic main lodge has not changed much since Teddy Roosevelt stayed there in 1906.

In Friday Harbor, you'll find museum-quality art by Northwest Native Americans at the Arctic Raven Gallery and a rich trove of local history around the corner at the Griffin Bay Bookstore. Just up the street, the nonprofit Whale Museum posts a daily log of orca sightings, as well as a brief guide to responsible tour companies. Inside the museum, you can eavesdrop on orcas via live audio, listen to humpback recordings, or learn to visually identify local whales by their distinctive saddle patches and by the shape of their dorsal fins (hint: Ruffles has ridges).

Still, nothing beats a seaside encounter with the live creatures, preferably in the late afternoon. "The light is beautiful then, and we've already been out on morning runs, so we have a good idea of where to find the local pods," explained Jim Maya, captain for Maya Whale Watch Charters.

We saw orcas within 10 minutes of boarding Maya's six-passenger boat. Members of J-pod, the most gregarious of the residents, cavorted a hundred yards away, rising out of the water in circusworthy "spy-hops" to get a better look at us. They slapped their flukes against the surface, did barrel rolls, and raced each other. "Just general horsing around," Maya said.

I would have been happy there for hours, but just then, a scratchy radio call came in from a Canadian tour boat a few miles away; it was a friend of Maya's who works out of nearby Victoria. He'd just spotted 50 orcas he didn't recognize—a shy tribe of fish-eating "offshores." We zoomed near his boat and turned off the engine.

After a minute, we saw them too: dozens of black-and-white animals pulsing past us through the water in shallow leaps. They sliced the waves in parallel formation, a long, dancing line of proud dorsal fins, each fin five or six feet high. "A wall of whales," somebody said as they passed, but to me they seemed a graceful chorus line of husky June Taylor dancers wowing the crowd.

Nobody talked. We stared. The only sounds were water sloshing against the hull and that deep, reverberating sigh of each whale. Finally, a Canadian voice crackled over the radio. "Wow. Eh?"

Wow-eh, indeed.