National Weather Service (NWS) forecasters in Hawaii issued a high surf warning on Friday, warning swimmers to dangerous waters.

The advisory is in effect for all eastward coasts of Hawaii through Saturday evening, including Olomana, Maui Windward West, Kauai East, Koolau Windward, Molokai Southeast, Windward Haleakala, Big Island East and Big Island North as “moderate to high, medium.” period swelling produces surf at consultative level.

“Surfs are expected to peak this afternoon into the evening, then slowly subside over the weekend,” the advisory said.

A swell is a series of waves produced by storm winds.

NWS meteorologist Dennis Trotter said Newsweek that it is typical for waves in Hawaii to intensify during the transition into the winter season.

Ola is not associated with Hurricane Kristy, a Category 3 storm with maximum sustained winds of 115 mph in the eastern Pacific. Trotter said, however, that there could be an increase in wave height early next week because of Kristy, although it’s too early to tell if it will affect Hawaii.

The National Hurricane Center (NHC) anticipates that Kristy will experience “steady to rapid weakening” over the next few days. Earlier this week, the storm experienced rapid intensification and quickly became a major hurricane. Thursday night, Kristy was a category 5—the strongest storm on the planet.

The NHC forecast anticipates that Kristy will became a post-tropical cyclone Sunday. The storm is not expected to make landfall, but will likely cause dangerous swells in other parts of the region.

“Swells generated by Kristy are affecting portions of the west coast of the Baja California peninsula and will likely continue to impact the region through the weekend,” the forecast said. “These swells can cause life-threatening surf and break current conditions. Please consult (warnings and alerts) from your local weather office.”

In addition to the high surf advisory, forecasters also issued a marine weather statement for windward waters in Maui County and the Big Island Friday morning.

“A period of average swell of 6 to 8 feet NNE from 010 to 030 degrees will fill in quickly today and peak this afternoon into the evening,” the statement said. “This swell could produce waves in north-facing harbors, primarily Hilo and Kahului harbors. Mariners using these ports should exercise caution when entering or leaving the port and when berthing or launching vessels.”

A marine weather statement was also issued for waters near Southern California as dense fog was forecast to affect the coast of Los Angeles and Orange counties, the Santa Barbara Channel and “coastal waters around Point Conception southward through the southern exteriors” through Saturday morning.