Fog makes up a significant part of climate here in wine country. It is what makes summer nights into cool evenings. The ripening grapes benefit from the marine fog intrusion by cooling down the vineyard. The temperatures, typically in the 90s during the day at the hottest point, quickly cool down to 50 degrees or so because of the fog.
Today I’ll be talking about the two types of fog we have here in California: radiation fog and advection fog. The first type comes in the wintertime and the second in the summer. In fact it is the cooling down of the vineyards from the advection fog in thanks to the marine influence just 30 or so miles to our west combined with a deep crevice along our Sonoma Coast making the water even colder hence creation of this type of summer morning and evening fog.
Advection provides us with Tule Fog-famous in Sonoma County in my younger days for blanketing the stretch between Healdsburg and Windsor, the town to the south. I haven't seen much of it in the last decade or so in this area although while out on my walk at 6am today there was quite a layer-obliterating the waning moon. You find it mostly situated in and around San Francisco. I found a video of it for you here by our local ABC news station. The vines don’t need much cooling in the winter but the beauty of it is indeed striking.
Remember Carl Sandburg’s poem Fog?
The fog comes
on little cat feet.
It sits looking
over harbor and city
on silent haunches
and then moves on.
I think this is the perfect image of winter fog. A toast to our unique California climate and all that it brings to our wines!
The photo below captures the winter fog as the vineyard crew prepares for erosion control measures.