Semi-Unusual June Rain: Bay Area Precipitation Totals

A color-enhanced infrared image of a storm moving into the Pacific Northwest early Wednesday. The system is expected to bring rain to most of the Bay Area on Thursday. (NASA Earth Science Office)

Update, 10:35 a.m. As advertised by human forecasters and their numerical weather models, this morning's rain has been heaviest north of the Golden Gate, with mostly light -- very light -- totals to the south and east.

Here are 28 locations in the greater Bay Area (and slightly beyond) and their rainfall totals through 10 a.m.:

Location Rain amount
Mount Tamalpais Middle Peak 0.58
Dillon Beach (Marin County) 0.40
Venado (Sonoma County) 0.40
Olema Valley 0.39
Point Reyes 0.25
St. Helena 0.24
Santa Rosa-Charles Schulz Airport 0.22
Sacramento International Airport 0.22
Angwin (Napa County) 0.20
Napa Airport 0.20
Mill Valley 0.19
Mount Veeder 0.19
Point Reyes Station 0.19
Barnaby (West Marin) 0.17
Kentfield 0.11
Novato Library 0.08
San Francisco 0.05
Vacaville 0.05
Vollmer Peak (Berkeley Hills) 0.05
Half Moon Bay 0.03
Lake Berryessa 0.03
Oakland Int'l Airport 0.02
San Rafael 0.02
Briones 0.01
Orinda Fire Station 0.01
Rodeo 0.01
SFO Int'l Airport 0.01
Concord 0.01

Original post: The Bay Area is in for a semi-unusual weather event beginning early Thursday: June rain.

We say semi-unusual, or perhaps quasi-atypical, because while rain in June is a relatively infrequent occurrence in most of California -- with no precipitation recorded in 53 of the 167 Junes in the San Francisco weather record -- it is not at all unheard of.

It last rained in June all the way back in 2015, when San Francisco got .01 of an inch on the 1st of the month and .11 on the 10th. The last June you might call rainy was in 2011, when the city recorded 2.02 inches, including .99 on June 4 and .81 on June 28.

Part of the Daily Alta California's June 14, 1884, account of heavy rain and crop damage throughout California. (California Digital Newspaper Collection)

We'll get back to the historical record after taking a look into the immediate future.

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The National Weather Service Bay Area forecast office says rain should sweep from north to south through the region starting before dawn in central Sonoma County. Precipitation is expected in the central Bay Area by the morning rush hour and wrapping up later in the morning in the South Bay.

How much will fall? About half an inch in the wettest North Bay locations and a quarter-inch or less for the rest of the region. The forecast calls for showers to end by Thursday evening and for Friday to be partly cloudy and unusually humid.

Revisiting June rainfall history: The wettest June on San Francisco's long rain record occurred in 1884. The city's downtown gauge measured 2.57 inches that month.

Then as now, the local media had an outsize interest in what seems like relatively mild atmospheric events. But whereas today the main focus of weather reporting is on travel impacts, the rain's effect on the state's crops got most of the attention in 1884.

Wheat was California's biggest crop in the 1880s. Lots of acreage was planted in barley and hay, too. The grain crops were vulnerable to being "lodged," or beaten down, in the downpours that swept the state. New-mown hay was liable to rot in the fields.

San Francisco's Daily Alta California reported bad news from farm districts throughout the state. A correspondent in Merced, in the San Joaquin Valley, wrote "the wheat fields are indeed a woful [sic] looking scene to look upon."

From Oroville came news "that hundreds of tons of hay is rotting in the fields, and thousands of acres of the harvest grain lies flat and cannot be harvested. The present outlook is very gloomy for the farmers." The Napa Valley's hay crop was said to be close to a total loss.

The Sacramento Union reported the late rain had ruined the season's cherry harvest.

But the Union said Sacramento County was a bright spot amid the state's dismal farmlands, with corn and alfalfa and other crops doing well after the rains. And the county had good news for breweries, too.

"The hop men are highly elated over the prospect of an abundant crop and the assured fact of excellent prices," the Union said, estimating the counties' crop of hops would total 3.6 million pounds and bring growers nearly three-quarters of a million dollars.