Waters off the Marin coast are particularly cold this year, and scientists say it’s thanks to the third consecutive year of La Niña—a process that causes periodic cooling of ocean surface temperatures in the central and east-central equatorial Pacific. Earlier this month, the Bay Area’s National Weather Service recorded the coldest surface water temperature off the coast of Bodega Bay since 2012, at around 47 degrees. That compares to an average of 51 degrees for June. Temperatures often fluctuate; as of Wednesday, water temperatures were measured at 50 degrees at Bodega Bay and 51 at the Point Reyes buoy. La Niña is associated with stronger upwelling, a phenomenon caused by high winds that bring cold, nutrient-rich water to the surface, creating favorable conditions for fish and fisherman. The weather pattern typically occurs every three to five years, but it can happen successively, as it has the last two years. Scientists say this year’s event will likely continue into the winter.  Willy Vogler, co-owner of Lawson’s Landing, said that fishermen have seen large amounts of krill in the past week, which means more food for fish. At the same time, the exceptionally cold waters compared to years past could be bad for fishing conditions. “As a fisherman, it seems like I do better catching when the water is up in the mid-50s,” Mr. Vogler said. “I think [fish] get a little more active when it’s warmer.” Marisol García-Reyes, a principal scientist at the Farallon Institute, said that last year saw record-breaking upwelling thanks to high, persistent winds, whereas this year’s winds are more intense but less frequent. In May, the Point Reyes National Seashore recorded wind speeds at the observation deck above the Point Reyes Lighthouse at a peak of 85 miles per hour. Ms. García-Reyes said that although La Niña is typically good for the ocean, it is also associated with variable rain patterns and dryness on land. At sea, despite strong upwelling and the other impacts of La Niña, Ms. García-Reyes said scientists aren’t seeing water temperatures decrease over time in Central and Northern California, since any decreases are being offset by warming seas. “This is probably a battle between the increasing global temperatures of the ocean and the upwelling that makes [waters] cold,” she said.