Depending on where you live along the axis of Terra Firma’s delivery routes, right now you are either basking in warm and sunlight, or shivering in the cold fog. Here at the farm, we haven’t seen the sun in a week and even then it was just brief glimpses. The thermometer has been pegged at 45 degrees — day and night — and every morning we wake to a heavy dew that takes hours to evaporate if it does at all.
Even if you’ve never lived anyplace that has it, you’ve probably heard about Tule Fog — a completely different animal entirely than the summertime marine fog that keeps the Bay Area cool most of the time in the summer. Tule Fog occurs when rain is followed by high pressure that shuts down air movement and holds the humidity close to the ground. It always happens in winter, because the low sun angle, chilly temperatures and short days don’t allow for the fog to burn off entirely, and it can last for weeks at a time.
Tule Fog is a Central Valley phenomenon. Cold, damp air gets trapped in the bathtub-like valley and sloshes around. If it gets deep enough, it can flow west out into the Bay and reach parts of the Bay Area when there is no wind coming off the ocean or if there is an east wind. But it rarely sticks around 24/7 for days there like it does here.
The winter Fog doesn’t happen if frequent storms keep the air moving, nor during dry winters as we often experience during droughts — especially when we have dry offshore winds. Thus, it has been relatively rare in the last 20 years, which seesawed back and forth between very wet and very dry winters. Prior to that period, it happened almost every year since I arrived here in 1993 — usually in December.
December is the month when the growth of most our crops slows to crawl anyway, as it is generally the coldest time of year with the shortest days. It’s also usually one of the wettest months, which means limited sunlight for the plants. This year, we’ve yet to have a drop of rain in December, but we got so much rain in October and November that you’d never know. The fog is keeping everything damp, muddy and covered in water.
After Thanksgiving, we were a bit concerned about our upcoming two-week vacation at the end of the year. The rain and relatively warm temperatures in the Fall had encouraged all our crops to grow quickly, and we were looking at the possibility that some of them might need to be harvested before New Years. The arrival of the fog took care of that problem. Now, the vegetables growing in the field may as well be in our refrigerated coolers, which are kept just a few degrees colder than the ambient outdoor conditions right now. Without sunlight and warmth, they have essentially gone dormant — exactly what we want them to do while the farm is closed.
In the meantime, we still have a few things left to harvest for you. But no one is accustomed to the cold yet: working outside when it’s 45 degrees and 98% humidity with no sunshine is bone-chilling. The plants are covered with water, and by the end of the day our crew is cold, wet and tired. When we finish work at 3:45, it’s already almost dark thanks to the fog gloom.
Next week will be our final CSA box delivery of 2025. Thanks to the placement of the holidays this year, we will not be altering our delivery schedule. We will resume deliveries on January 7th, by which time we hope the fog will have cleared out a bit and the crops have grown slightly.