Expect another bountiful crop of blue jellies this year along West Coast beaches.

Billions of "by-the-wind sailors," also called Velella velella, could wash ashore in coming months because of favorable water temperatures and onshore winds, scientists say. People have already spotted thousands of the baseball-size creatures at beaches from Washington to Southern California. A gargantuan number of the stunning sea sailors were also blown onto western beaches in 2014.

Velella are outfitted with a stiff, chitinous sail that catches the breeze like a ship does. Because the sail angles against the eastern Pacific's prevailing northwesterly wind, the little blue sailors usually tack offshore. Clusters of them are commonly seen drifting at sea. But when the winds shift to the southwest, as in late winter and spring, the masses may be blown onshore to rot and die.

While some Velella always wash up on West Coast beaches each spring, the unusually large numbers seen in recent months may be connected to warm water off North America, said Dave Checkley, a professor at the Scripps Institution of Oceanography and director of the California Cooperative Oceanic Fisheries Investigations program. [Album: Amazing Photos of Jellyfish Swarms]

A huge blob of warm water has been parked off the West Coast for months, and a budding El Niño is also spiking ocean temperatures off California. The Velella clusters could be following these warm currents, or perhaps a by-the-wind sailor baby boom is in effect. With a life cycle of less than a year, the Velella must quickly reproduce to take advantage of plentiful food.

"When warm water invades our part of the world, Velella commonly comes with it," Checkley told Live Science. "It's really quite fascinating, so I say enjoy it. They're part of nature and they're beautiful."

Velella float on the ocean surface, drifting with the winds. Though the creatures are not true jellyfish, they fill a similar role in the ocean and are also in the phylum Cnidaria, as are jellyfish, coral and sea anemones. A Velella's electric-blue body hangs down into the water, with stinging tentacles that capture small prey such as tiny shrimp and plankton. The blue color provides protection from the sun's ultraviolet radiation, Checkley said.

In the ocean, floating snails, sea slugs and sunfish will gobble up the gelatinous creatures for meals.

Although Velella toxins are harmless to humans, it's not a good idea to handle the jelly creatures and then touch your eyes or mouth. The Velella neurotoxin might cause itching.

Checkley said beachgoers shouldn't miss this opportunity for a close look at an unusual sea creature. "Put them in some water and see how the tentacles hang," he said. "Try to figure out who might they eat and what might eat them. They're not going to hurt you."

Follow Becky Oskin @beckyoskin. Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.