SAN FRANCISCO (AP) — Umbrellas were out and streets were slick in the San Francisco Bay Area on Monday as a rainstorm ushered in a two-day wet-weather system heading from the Pacific to the Sierra Nevada.

The system moving across California is bringing cool, wet weather to the lowlands and snow in the mountains. The welcome rain will not end the state’s four-year drought, but forecasters expected a strong El Nino winter to bring above-average precipitation in parts of the state.

Chains or snow tires are required on most mountain highways around Lake Tahoe on the California-Nevada border, with the forecast calling for up to 7 inches of snow along the Sierra Nevada mountain pass and up to 1½ feet at the highest peaks through Monday night.

The National Weather Service in Sacramento says a low-pressure system from the Gulf of Alaska is expected to drop up to three-quarters of an inch of rain in low elevations in California.

Temperatures in the San Francisco Bay Area and central California are expected to dip into the 40s, and winds could reach 10 to 20 miles per hour.

Thunder and lightning is expected in some areas, and some thunderstorms may produce hail. A dramatic photo of a cloud-shrouded Golden Gate Bridge shows lightning striking Monday over the iconic span.

The weather will turn chillier Tuesday, with temperatures in some inland valleys dropping into the low 30s. Patchy frost will likely collect in the coldest areas around the San Francisco Bay Area, so residents are urged to bring plants and animals inside.

The remainder of the week will stay dry, but cold and rain is expected in the San Francisco Bay Area by Sunday. Rain also is forecast along the Central Coast and in Southern California.