Quick answer
Keep the drying room at 55-62% relative humidity (RH) and 60-70°F. The common baseline is 60% RH and 60°F. Do not drop below 45% RH or the buds dry too fast and lose terpenes. Do not rise above 65% RH or mold and mildew become likely. Measure RH at canopy height, not at the wall or floor.
humidity control during cannabis drying
Why humidity matters
Humidity controls how fast water leaves the plant. Slow drying lets chlorophyll break down and preserves cannabinoids and terpenes. Fast drying traps chlorophyll, creates a harsh smoke, and can leave the interior wet. High humidity stalls drying and invites Botrytis and powdery mildew.
Prerequisites
- Calibrated hygrometer and thermometer
- Dehumidifier and humidifier sized for the room
- Small circulation fan that does not blow directly on buds
- Drying racks or lines in a dark room at 60-70°F
- Moisture meter or jar hygrometer for the cure
Step-by-step setup
- Hang whole branches or place buds in single layers on racks. Keep buds from touching.
- Place the hygrometer at canopy height in the middle of the room.
- Set the dehumidifier to 60% RH and the humidifier to 55% RH.
- Run the circulation fan on low, pointed at a wall or floor, not at the plants.
- Check the hygrometer twice daily and adjust the dehumidifier or humidifier by 1-2% RH.
- Record temperature and RH each morning and evening.
Target humidity by drying stage
- Days 1-3: 58-62% RH. Buds are wet and mold risk is highest.
- Days 4-7: 55-60% RH. Water leaves the stems and outer flower.
- Days 8-12: 52-58% RH. Small stems begin to snap.
Signs humidity is too high
- Stems bend without snapping after 10 days
- Buds feel damp or spongy
- Hay or ammonia smell
- White fuzz or gray patches
Signs humidity is too low
- Stems snap in 3-4 days
- Buds crumble when squeezed
- Outside is dry and brittle while inside stays wet
- Harsh, tickly smoke after cure
Transition to curing
When small stems snap and larger stems bend, trim and place buds in jars. Target 58-62% RH in the jar. Burp jars twice daily for the first week if RH rises above 62%. A stable 60% RH in the jar means the dry is complete.