RELATED: Mount Diablo gets dusting of snow
A Winter Weather Advisory has been issued for elevations above 1,000 feet in the Bay Area from late Monday afternoon through Tuesday morning.
Rain turned to snow as light flurries began falling and sticking to the ground just below 4,000 feet.
"So far this year, it's been the most I've seen," said Rocky Francisco who works at Lick Observatory.
At 4,200 feet, the intensity of the snow picked up.
"Started coming down pretty good right about 10 am. We get snow a couple times a year, this isn't the most I've ever seen but if the forecast holds true, it might be," said Joe Halay, facilities supervisor for the observatory.
Snow hitting the peak of Mt. Hamilton is not rare but when it happens, it's always a spectacle to see.
RELATED: Snow falls atop Mount Hamilton, Diablo with dusting possible on other Bay Area peaks
"It's beautiful but it's dangerous. I certainly don't encourage anybody to come up to the observatory to play in the snow," said Halay. "This is not a snow park. We're not equipped to handle it."
Even though the observatory is closed until Wednesday, snow plows worked nonstop to clear the winding roadways around the area.
With more snow expected to fall on Mount Hamilton overnight, things might get messy for people heading up the summit.
Watch the latest AccuWeather forecast and take a look at recent weather stories and videos.