The weather service does not have cameras tracking snowfall but alertwildfire.org does and shows a considerable amount of snow on Mt. Hamilton, located in Santa Clara County and home of the Lick Observatory.
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Snow was still falling at 8:22 a.m. By the end of the day Wednesday, as much as a foot could be atop that peak and others.
"It's going to be cold out there," meteorologist Roger Gass said.
Elevations above 4,000 feet will be cold enough that by Wednesday the total accumulation of snowfall could be significant, Gass said.
Sunday night into Monday, snow may have fallen on peaks as low as 3,500 feet, weather officials said.
Some peaks above the Big Sur coast are also likely to have seen snow.
"Those typically turn into a winter wonderland," Gass said.
Gass said the unsettled weather is expected to continue through Wednesday.
NWS tweeted map of where snow will fall this week: