Daniel Swain in KQED: Bay Area Logs Especially Wet May

“The weather pattern literally looked like something straight out of January, but it’s May,” said Daniel Swain, a climate scientist with UCLA. “This regression back towards winter like conditions is amazing. There was a significant amount of rain near the coast.”

It was San Francisco’s 12th wettest May on record, according to the National Weather Service. The agency’s records show 2 inches of rainfall collected at San Francisco International Airport in May, the most since 1998, when 2.37 inches fell there.

The cause of all the rain is an unusually strong jet stream located farther south than normal, Swain said.  The rain is even stranger, Swain added, because the region’s long-term trend is towards drier springs. “This May really stands out as an outlier from that perspective,” he said.