For most of the year, fog hugs the California coast. It’s a morning phenomenon, burning off by midday.

However, from November to March, the combination of warm moist ground blanketed by cold, still air creates Tule fog a thick ground fog that settles into the Sacramento and San Joaquin Valleys and pushes west toward the coast where it seeps into valleys before being blocked by coastal hills.

Tule fog is thickest in December and early January. Think Sherlock Holmes’ London-thick. At times even street lamps or headlights cannot cut through it for more than a few feet.

Horrid stacks of vehicles come to screeching, cataclysmic collisions when it is at its worst. The CHP advises:

• Check weather reports before driving on highways during Tule Fog months;
• If you know it will be foggy, consider delaying your trip until it clears;
• If you’re on the road and run into fog: drive with headlights on low beam (high beams create a wall of white light that keeps you from seeing ahead);
• Watch for CHP pace cars to guide you;
• Avoid crossing traffic lanes;
• The denser the fog the slower you should go (if you can’t see more than three lane stripes, move to the right and slow down);
• Drive with the driver’s window open to hear traffic ahead;
• Stay in a lane, don’t straddle a line (if you can’t see the lane stripes, it’s too unsafe to drive – get off the highway);
• Move around stalled or stopped vehicles, don’t sit behind them;
• Do not stop on highways except in emergencies; and
• If you must stop or your car is disabled, don’t stay there. Move to the far right shoulder of the road and get off the roadway, turn off all lights and get everyone out of your car and far from it (common fatal accidents in fog are caused by speeding drivers attracted to follow whatever tail lights/car they see ahead, even if it is stopped).

Bay Area color spotter Darrell Sano decided to take one of his favorite hikes today. What he didn’t expect was that he’d be in the thick of it.

The sun struggled to burn through the cloudy atmosphere. As he drove through the Caldecott Tunnel toward Martinez, “a band of fog diagonally covered the homes above the highway. Once through the tunnel, the fog was even thicker.” he wrote … the opposite of the Bay Area’s usual fog pattern.

At Briones Regional Park, the air was damp with fog, with no chance at all to view the vistas that once topped surrounding hills, though his aerosolic envelopment made the hike all the more special.

Darrell found the last remnants of fall color carpeting the woodland floor, mostly ochre, without saturation, Past Peak, though still beautiful.

Though obscured by fog, faint color, subdued but still evident, could be seen. 

Apparitions emerged, a distant hiker, cows cloaked by mist, heard mooing but rarely seen.

As he walked through the diffused air, he thought about his last hike in August along the same trail and how different it was, realizing that our search for fall color is often filled with unexpected surprises. 

• Briones Regional Park, Martinez – Past Peak, You Missed It.