Skyline Fog

Published Cycle California, September 2014, Vol. 20, #8

The fog comes on little cat feet
It sits … on silent haunches and then moves on.

— Carl Sandburg, writing about San Francisco

Skyline Ridge, the towering fog bank is more like a mountain lion.  The Bay Area is said to have a Mediterranean climate.  Athens and most of Sicily are about the same latitude, but without the fog bank particular to the peninsula.  The northwest seabreezes that blow along the coastal range draw surface waters away from the mountains, causing deeper and colder Pacific Ocean currents to rise.  The hot, interior valleys draw inland the warm, moist ocean air, which condenses over the cold water, often covering all the Golden Gate Bridge except to the top of the two towers.

Visible from I-280 to the south along the Crystal Springs Reservoir, a humongous white wave above the mountainous spine often perches ready to crash down.  During the day, the fog stays put while the air flows through.  Skyline Boulevard begins at windswept Highway 92, about 850 feet above sea level.  As the road continues southward, there are three ways to road bike up from Woodside below.  Kings Mountain and Old La Honda roads are narrow but often with little traffic.  Between them is two-lane but shoulderless Highway 84, frequently hectic with cars, connecting with Skyline’s low point at Skylonda.  You can leave the dry and sunny mid-Peninsula area and soon find yourself in a cold and dripping wet forest, deeply regretting not having your windbreaker along that you optimistically left behind.  Those glorious redwoods are remnants of ancient geologic periods, think Jurassic, and continue to thrive along the coastal slopes.  Near Skeggs Point is the Methuselah Tree, a redwood over 1800 years old, think Roman Empire at its height.  Past Old La Honda Road, redwoods give way to the barren crests of Windy Hill and Russian Ridge.  The ridge cloud usually peters out around Page Mill Road as the distance to the coast has increased and the land’s elevation risen.

The mystery for bikers is always what the conditions are like on the ocean side of Skyline.  Often you can descend Old La Honda Road through the gray curtain to see a glorious, sunny landscape below.  At other times, you can bike through sunshine all the way to within a half-mile of the San Gregorio Store and into a fog blanket obscuring the sun’s radiation.
During the day, as temperatures rise inland, onshore winds begin to howl. If you’ve left Belmont turning south on popular Cañada Road, you can gratefully catch a tailwind, albeit a cool one, gushing over the Highway 92 gap.  You’re sailing around 25 mph while those approaching on the other side of the road are struggling to meet half that speed.  The 20-30 mph winds also make for good viewing of kite-boarding if you’re biking the Foster City shoreline bike path.  Meanwhile along the coast, if you’re doing a Gazos Creek loop on Highway 1 back to Pescadero, you might be struggling against a riptide of air.

Dealing with the wind produced by nature’s air-conditioner seems a small price to pay, however, for the cool flow that’s provided during the summer swelter.  That feature is often taken for granted except those rare weeks, usually one in June and one around October, when the coastal and inland valley pressures equalize and Bay Area bicyclists suffer in