Late flower humidity targets that actually matter

Once you hit week 6 of flower outdoors, your margin for error on humidity gets razor thin. I shoot for 45-50% RH during the day and I get nervous any time it climbs past 55% at night. In the PNW that second number is the hard one. Nights get cool and wet fast in September and the buds are dense enough by then to hold moisture for hours after a rain event. The thing most people skip is checking the humidity inside the canopy, not just ambient. Stick a cheap sensor down in the middle of the plant. It will read 10-15 points higher than what your weather station says. That gap is where botrytis starts. Air movement is honestly more useful than any spray at this stage. I run a small box fan on a timer overnight pointed into the canopy on a low setting. It does not have to be aggressive, it just needs to break up that stagnant air sitting between the colas. If rain is coming and you have portable plants, move them under cover the night before, not the morning of. By morning the damage is already done. For in-ground plants I use a simple lean-to tarp setup that still allows airflow on the sides. Trapping heat and killing airflow under a tarp is almost as bad as the rain itself. I also start pulling any fan leaves that are crowding bud sites around week 5. Not a heavy defoliation, just opening lanes for air to move through. Keeping the inside of that plant dry is the whole game this time of year.

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