Cold, dry Santa Ana winds swept across Southern California as overnight temperatures in some areas dropped below freezing.
"It's been very dry, which has helped the temperatures at night to get really cold," Ryan Kittell with the National Weather Service told KPCC, "though it is December — this is the time of the year we get those type of temperatures."
Drivers were urged to use caution Monday in mountain areas, where gusts could top 65 mph. The National Weather Service issued wind warnings and advisories for swaths of Ventura, Los Angeles and Orange counties.
Kittell said that the coldest air is typically near the surface, with warmer air above it, so wind actually helps mix those up and keeps temperatures more moderate.
"Kind of like putting Ovaltine in your milk," Kittell said. "If you don't mix it up, you can tell where it all sinks to the bottom and where all the Ovaltine sits, and you can tell where the milk is, but if you start stirring it up, it mixes it all up, and that's kind of what happens in the atmosphere."
Freeze warnings were set to expire as daytime temperatures inched up into the 60s.
"We had some freeze and hard freeze warnings out for those interior areas," Kittell said, "and we might have a few more of those for tonight's temperatures as well. And that's mostly for highlighting the impacts to vegetation and plant life whenever you get subfreezing temperatures, and a hard freeze warning means that you could get that in addition to potential pipe bursts for any outdoor exposed pipes, because the water freezes solid and expands and can cause damage."
A record of 17 degrees was set in Lancaster early Sunday. In Santa Maria, it hit a record 27 degrees.
"It feels a lot colder because it's so dry," Kittell said. "Because it's so dry, it wicks away and evaporates any moisture on your skin, and just makes it feel colder."
There's a chance we'll have a wet Christmas, Kittell said, but computer projections this far out remain uncertain. Temperatures are are expected to warm up by Wednesday before cooling down again toward Christmas.
To the north, patchy freezing fog is forecast for early Monday in Sacramento, where temperatures dipped below 30 degrees overnight.
A freeze warning was also issued by the National Weather Service for the San Joaquin Valley.
This story has been updated.