SAN FRANCISCO (CBS SF) — Smoke from the Sand Fire, centered near the towns of Guinda and Rumsey in Yolo County, has been reported Saturday night over Marin, Solano and Sonoma Counties and even helped make sunset over San Francisco more dramatic than usual.

Smoke from the Sand Fire — which, by 9 p.m. Saturday had spread to about 1,700 acres with zero containment — comes after a combination of expected sizzling temperatures, light winds and vehicle exhaust prompted the Bay Area Air Quality Management District to declare the first Spare the Air smog alert of 2019 for Sunday.

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More than 500 firefighters had been sent by Saturday night to fight the Sand Fire, which was first reported at 2:50 p.m., Cal Fire said Saturday. No structures had burned as of 9 p.m. Saturday but residents of Yolo County Road 41 north of Rumsey have been ordered to evacuate, Cal Fire said.

The entire Bay Area will be under a “red flag warning” throughout the weekend.

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“That means that we have exhaust from millions of automobiles, combining with hot inland temperatures, low wind and that’s creating a smog situation,” said Ralph Borrmann of the Bay Area Air District. “So we’re asking Bay Area residents to reduce driving if they possibly can tomorrow.”

There were 13 spare the air alerts during the summer last year.

The district says Livermore Valley and south Santa Clara County have high ozone concentrations so people should limit their exercise until later in the evening. People with respiratory and heart conditions should also be mindful of their activities.

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