Many residents of Southern California awoke to subfreezing temperatures on Tuesday as a combination of weather factors brought a big chill to the region.

In the Antelope Valley, a low of 21 degrees was recorded in Lancaster, and Palmdale dropped to 28 degrees, according to the National Weather Service reports.

Elsewhere in Los Angeles County, Santa Clarita and Castaic hit 32 degrees, while the morning low in Woodland Hills and Agoura Hills was 31.

In Ventura County, some of the lowest readings included Thousand Oaks (33 degrees) and Ojai (31 degrees).

In the Inland Empire, Temecula saw a morning low of 30 degrees and Hemet dropped to 32.

Lows in the mid to upper 30s and low 40s were more common across Southern California, including the Los Angeles Basin, San Gabriel Valley and Orange County.

Shadowed canyons and high mountain communities were naturally cooler.

Why is it so cold?

While Southern California is no stranger to cold winter weather, these overnight lows are significantly below averages for January.

According to KTLA 5 News meteorologist Henry DiCarlo, there are two main reasons.

“We’re getting a northerly flow of cold air, and we had a passing cold front that raced off to the east,” DiCarlo explained on KTLA 5 Morning News. “Even though the cold front is long gone, the northerly flow is keeping cold air around with no blanketing effect from cloud cover.”

Temperatures could drop even further, DiCarlo says, before more seasonal norms return late in the week.

Overnight lows below freezing are expected again Wednesday, Thursday and Friday mornings, particularly in the inland valleys and high desert.

Tuesday Morning Low Temperatures (NWS):

  • Agoura Hills = 31
  • Anaheim = 43
  • Castaic = 32
  • Calabasas = 38
  • Corona = 37
  • Costa Mesa = 43
  • Downtown Los Angeles = 42
  • El Monte = 39
  • Hemet = 32
  • Lake Elsinore = 34
  • Lancaster = 21
  • LAX = 43
  • Long Beach = 44
  • Ojai = 31
  • Ontario = 36
  • Oxnard = 38
  • Palmdale = 31
  • Palm Springs = 39
  • Rancho Cucamonga = 38
  • Reseda = 36
  • San Bernardino = 35
  • Santa Clarita = 32
  • Santa Monica = 41
  • Simi Valley = 35
  • Temecula = 30
  • Thousand Oaks = 33
  • Torrance = 42
  • Victorville 28
  • Woodland Hills = 31