It was July 8, 1974, and San Franciscans didn’t know the storm was coming. 

It surprised unsuspecting office workers caught without umbrellas as they walked onto the drenched city streets that morning. By noon, over half of an inch of rain had fallen, and the rest of the Bay Area was just as unprepared. It caused widespread traffic jams across the region, already exacerbated by striking AC Transit bus drivers, with cars coming to a standstill after a semi-truck crashed just east of the Bay Bridge toll plaza. 

Then there was the flooding. Panicked baseball fans delivered a tarp to the Oakland Coliseum as they fretted about the cancellation of that evening’s game against their Cleveland opponents, billed as ex-Giant Gaylord Perry’s effort for an American League record of 16 victories in a row, the Examiner reported at the time. Farmers winced as they looked up at the sky, dreading the relentless downpour’s devastating impact on their upcoming harvest.

It turned out to be the wettest July in San Francisco’s history with a total accumulation of 0.72 inches of rain — 0.53 inches of which fell during that 24-hour period, Matt Mehle, a meteorologist for the National Weather Service’s Bay Area office, told SFGATE. Over 50 years later, this month could be set up to join it in the city’s weather record books.

That is, “if we pick up a few more days of drizzle,” Mehle said.  

San Francisco has had four days of rain amounting to seven hundredths of an inch of precipitation so far this month. One more hundredth of an inch would put this July on track for being among the top ten rainiest Julys on record, breaking the eighth, ninth and tenth place rankings, all of which are currently tied from 1906, 2011 and 2014, Mehle said. 

For those keeping score at home, San Francisco’s second-rainiest July was in 1886, clocking in at just under a quarter of an inch. The third and fourth place rankings are tied for 0.21 inches of rain measured in 1860 and 1975. The fifth place record stands at a tenth of an inch of rain in 1891, while sixth and seventh place are tied at nine hundredths of an inch of rain recorded in 2015 and 2022, according to Mehle.  

In terms of total days of measurable rainfall, the city could break a record if it reaches a fifth day, which would be occurring for the first time since 1850, according to the San Francisco Chronicle. (The Chronicle and SFGATE are both owned by Hearst but have separate newsrooms.)

"Confident" chances for more rain are highest Sunday night through Monday morning, Mehle said. 

If it’s seemed like an unusually gray summer in the Bay Area, it’s not just your imagination. Mehle said a couple of factors are at play, the first of which he referred to as a long wave pattern that’s causing the high and low pressure systems set up on the California coastline to shift slightly. “The high pressure that brings heat has been displaced a bit from its normal position, so we’re getting more troughs and low pressure over the Pacific Northwest and California to bring us more cool air,” he explained. 

The second is due to upwelling along the coastline, which has been bringing cold water deep in the ocean to the surface as prevailing winds off the coast of the Pacific Northwest blow over it. “What we’re seeing is like enhanced air conditioning over the shoreline,” Mehle said.   

Whether you like to embrace the gloom or have been withering without sunshine, Mehle noted that 150 million people east of the Rockies are living under a major heat risk advisory, and NOAA’s weather prediction center is eyeing a shift to warmer, more seasonable temperatures in the Bay Area by mid-to-late August. “So be careful what you wish for,” he said with a chuckle.

Mehle added that the hottest time of year for San Francisco is not in July and typically falls within the August to September time frame. Notably, the city recorded its all-time hottest day in September of 2017, when the mercury rose to 106 degrees. 

“It might not look like it right now, but summer is not over,” he said.