An unusually cold winter storm system brought snow to southern California, a sight so rare that the National Weather Service had to send out the definition of snow, freezing rain and sleet. Snowfall was reported in the neighborhoods of Calabasas, Sylmar, Northridge, Pasadena, Rancho Cucamonga and even Malibu, CBS Los Angeles reports.

Just before 1 p.m., snow was falling at the 1,500-feet level in the Santa Monica Mountains above Malibu, where Los Angeles County Fire Department Air Operations Section officials warned that roads there "will be slippery."

Correct, that is snow! Lots of confusion today. If precip bounces it contains ice - call it sleet or small hail. If precip in flakes it's snow, white balls are melted flakes called graupel. #CAwx #LArain #CAstorm https://t.co/Awdddmp7tc — NWS Los Angeles (@NWSLosAngeles) February 21, 2019

"Coming from Texas, and this being California known as heat and beaches and stuff, I wasn't prepared for this," visitor Chris Lambert told CBS Los Angeles.

Get Breaking News Delivered to Your Inbox

The city of Acton in the Antelope Valley was also briefly covered in snow before most of it melted by late morning, CBS Los Angeles reports.

The last time it snowed in downtown Los Angeles was in January 1962, according to the Los Angeles Times. The hashtag #SnowLA trended nationally on Twitter as everyone — including actors like Jerry O'Connell — posted photos and video of the snow.

"Calabasas, California, where the Kardashians live," O'Connell said in a Twitter video. "Look at this. Snow. Snow. Not hail. Snow."

#Snow in #ThousandOaks?! Students from Century HS, the medical department, and ESL all emerged from clasrooms to marvel at this unexpected phenomenon. #CAwx pic.twitter.com/3biHepXhQK — Amy Buss (@USArmyVeteran17) February 21, 2019

L.A.'s Office of Emergency Management even posted safety tips. Los Angeles Mayor Eric Garcetti tweeted that Boston Mayor Marty Walsh called him to offer snow plows and shoveling lessons.

My dear friend and brother mayor @marty_walsh just called from Boston to offer to send plows if the snow reaches our city. #staycalmLA and send pics from your neighborhood if you're snowed in. EG — Eric Garcetti (@ericgarcetti) February 21, 2019

But all jokes aside, the icy conditions caused two freeways to close down. The 5 Freeway through the Grapevine was closed in both directions early Thursday afternoon, according CBS Los Angeles.

Multiple collisions due to weather, meanwhile, were reported along Interstate 15 in both directions between Baker and Nipton, according to San Bernardino County Fire officials.