The skies in the Bay Area and other parts of Northern California glowed in a surreal light on Wednesday as smoke from various fires shrouded the region.
From San Francisco to Yosemite, social media was filled with images of menacing red and orange skies and smoky air.
The National Weather Service explained the conditions as follows: “When the winds in the air weaken, gravity will do the primary vertical transport of the smoke. Floating smoke rises closer to the surface and today it can cause darker skies and deterioration in air quality. "
The sky was so dark that a utility worker in Mountain View turned on his truck headlights while working on a fire hydrant Wednesday morning.
"The real problem is that the ashes are falling from the sky," said Fabian Rios, who was wearing a surgical mask when he was working on the hydrant. "I am currently covered."
UCLA climate researcher Daniel Swain said the smoke from the fire blocked the sun significantly.
"Extremely dense and high clouds of smoke from numerous large forest fires, some of which have produced nocturnal pyrocumulunimbus (" fire thunderstorms ") clouds, are almost completely blocking the sun in some parts of northern California this morning," he wrote on Twitter.
The Bay Area Air Quality Management District said air quality was unhealthy for all regions of the Bay Area on Tuesday and unhealthy for sensitive people in the northern and eastern regions on Wednesday.
The agency tweeted a statement for the orange and red skies on Wednesday, saying they were "a result of devastating smoke in the air. High winds in recent days have carried ash from fires in Northern California and Sierra Nevada to the region. These smoke particles scatter blue light, allowing only yellow-orange-red light to reach the surface, making the sky look orange. If the smoke becomes too thick in a certain area, most of the light will be scattered and absorbed before it reaches the surface, which can lead to dark skies. "
When the winds weaken in the air, gravity does the primary vertical transport of the smoke.
Floating smoke rises closer to the surface and today it can cause darker skies and deterioration in air quality. This is beyond the scope of our models, so we rely on your reports!
– NWS Bay Area (@NWSBayArea) September 9, 2020
The National Weather Service Office for the Bay Area said there is “an unprecedented amount of smoke in the atmosphere as a record number of acres burn in California and the west. From space you can't even see @KarlTheFog and the ocean layer as the smoke stretches far across the Pacific. "
Snapshots of a dark, orange Bay Area hit social media: San Francisco's landmark TransAmerica Pyramid, pointing into a sinister orange haze; Street lights turned on in front of the iconic Ferry Building on the city's waterfront; A dark orange mist wiped out the towers of the Golden Gate Bridge.
"The day the sun gave up in 2020 …" said one person's tweet over a video in Tiburon.
“The sun has been up for about an hour. We should have a sky with bright sunshine. It's so dark, ”tweeted Drew Tuma, a KGO-TV meteorologist.
The day before, the Bay Area had paused in the midst of a threatening but less apocalyptic sky as the smoke remained high in the atmosphere. But, as forecasters warned, gravity pulled the smoke closer on Wednesday.
The Bay Area is in the midst of the longest stretch of "spare the air" days – with its 23rd straight day on Wednesday – when regional air quality officials predict unhealthy air quality conditions.
The Bay Area AQMD has issued spare the air warnings since 1991. The longest episode of those days to date was a 14-day period in 2018 when the campfire broke through the town of Paradise and became the deadliest and most destructive fire in modern California history, killing 85 people and destroying more than 18,000 buildings.
The spare the air warnings are expected to last at least until Friday.