San Francisco took on a post-apocalyptic shade of orange, after smoke from Northern Californian wildfires reached the city on Sunday.

Just under a year since the deadliest firestorms in state history, intense wildfire has returned to the region, fanned by high winds and hot temperatures.

Smoke and ash from fires burning in the Yolo and Lake counties filled the sky about 75 miles south in the San Francisco Bay Area on Sunday morning, giving the city a foreboding orange filter.

The sky over San Francisco today from the Yolo County Fire.#countyfire pic.twitter.com/auVcITZomW — William Chamberlain (@chamberlainwill) July 1, 2018

San Francisco sky is bizarre right now. Rayleigh scattering through this cloud is depleting all the blues and leaving us with a sepia sky. pic.twitter.com/weUDCkulsN — Rick Zuzow (@RickZuzow) July 1, 2018

San Francisco Sky today. No filter. 😱 pic.twitter.com/0nfhFtq1yX — Alex Shyba (@alexshyba) July 1, 2018

San Francisco skies are scary looking from the Yolo County fire pic.twitter.com/SfYHQPtIaW — can (@can) July 1, 2018

Amber sky at dawn? There's a low cloud-layer/light fog in the air that's casting a very eerie light over San Francisco at the moment. Perhaps we're getting the smoke from a wildfire? Dust from Sahara?#TentOnTheRoof'InExile pic.twitter.com/gIfZHbjO1i — aHEMagain ❌ (@aHEM_again) July 1, 2018

Issuing a red flag warning, the California Department of Forestry and Fire Protection, or Cal Fire reports that mandatory evacuations have been ordered in Lake County, Napa County, and Yolo County, where California's famed Napa wine valley sits, since the blaze started on June 30.

As of Sunday evening on July 1, the flames had spread to an area of 32,500 acres.

On Sunday morning, the San Francisco Department of Emergency Management tweeted a warning for city residents, announcing the air quality in the city had changed to "moderate," and that older adults, children, or people with heart or lung disease "should consider reducing prolonged/heavy exertion." Everyone else, you're ok.

Advisory: San Francisco Air Quality is Yellow due to fires in the Lake and Yolo counties. People with heart/lung disease, older adults, and children should consider reducing prolonged/heavy exertion. #sf pic.twitter.com/QrrmaIAhSD — San Francisco DEM (@SF_emergency) July 1, 2018

The Pawnee Fire, located northeast of Clearlake Oaks within Lake County, has burned over 14,500 acres, but 73 percent has been contained at the time of writing. But across the Lake, Napa and Yolo counties, a total of just 2 percent of the 32,500 acre County Fire has been contained.

A high-resolution look at the #CountyFire smoke plume flowing SW atop the marine stratus layer. Taken by MODIS this afternoon #cawx pic.twitter.com/eBkt7M9LZ0 — NWS Sacramento (@NWSSacramento) July 1, 2018

According to Cal Fire, shifting winds have created numerous active portions of the fire that have the potential to increase the spread.

Stay safe, folks. Wildfire season is upon us.

Additional reporting by Mark Kaufman.