Northern California only has one date

Northern California gives outdoor growers something almost nowhere else does: a summer with essentially no rain. From June through September, the sky does nothing. Plants get full sun, low humidity, and no rot pressure worth worrying about.

Then October arrives and the whole season comes down to a single question. When does the first real rain show up?

Why that one date decides everything#

Through the dry months you can let a plant run. There is no reason to rush it, and the finishing weeks are when the flower actually fills. The limiting factor is not weather, it is patience.

That stops the moment the first Pacific storm comes through. A dense, nearly finished bud that takes an inch of rain and then sits in cool damp air is the ideal case for botrytis. Not a brush with it, the ideal case. Two days of that can turn a crop you have watched since April into something you throw away.

So the season has a hard edge, and the edge moves. Some years the first soaking rain is the last week of September. Some years it is the first week of November. That is a five or six week spread, and no almanac average will tell you which kind of year you are in.

What to actually watch#

Starting around September 20, look at two things every morning.

The first is the ten day forecast, specifically for a system with measurable rain rather than a marine layer or morning fog. Coastal fog is a separate problem and a chronic one. What you are waiting for is the first front.

The second is the plant. Where it is in its finish determines how much the forecast matters. A plant that is two weeks out has a real decision to make. A plant that is three days out does not, you just take it.

The two together give you the answer. Nobody can tell you in advance whether to pull on October 12, because it depends entirely on what is coming and how close you are.

The decision when both are in the middle#

The hard case is a plant that wants another ten days and a storm arriving in four.

You have three options and all of them cost something.

1. Pull everything now. Safe, and you give up the last stretch of filling and ripening. This is the right call more often than people want it to be.
2. Pull the tops, leave the rest. The upper colas are furthest along and most exposed. Taking them and leaving the lower canopy for a second pass after the storm clears often gets you most of the finished weight with much less risk.
3. Cover and ride it out. Works if the plants are in pots or small enough to frame. Does not work for a ten foot plant in the ground, and plastic draped on wet buds makes things worse rather than better.

The part people miss#

One storm in early October is often followed by two more dry weeks. Growers who pull in a panic at the first front sometimes give up a genuinely useful stretch of good weather.

The difference is whether the plants dry out afterward. If the sun comes back and a breeze moves through, the rot never gets established and you have bought yourself another window. If the gray sits, you were right to pull.

That is a judgment call you get better at and will not get right every year. What you can do is reduce the cost of being wrong: open up the dense colas before the storm, keep air moving underneath the plants, and go through the thickest buds carefully every morning for the week after. Caught at the first brown leaf, rot costs you one cola. Caught at the point where you can see it from across the yard, it has already taken the plant.

Why the rest of the country should not copy this#

Most of the outdoor growing material on the internet was written here, by people growing in this climate, and it quietly assumes a dry summer and a single October decision point.

If you are reading it in Georgia or Ohio or western Washington, that assumption does not hold, and following it will put you weeks behind where you need to be. The northern California calendar is the easy case. It is worth understanding that it is a local one.