For drying cannabis, keep the room at 45 to 55 percent relative humidity (RH). That is the single most important number. To hit it, buy a calibrated hygrometer first. Then add a small dehumidifier or humidifier with a built-in humidistat. This guide covers the features that matter, the exact parameter bands, and the mistakes that turn a good harvest into hay.
what humidity should be when drying cannabis
What to Look For in Humidity Control Gear
- Hygrometer: Look for a digital unit with plus or minus 2 percent RH accuracy and a display you can read from outside the tent. Calibrate it with a salt test before you trust it.
- Dehumidifier: Choose a model with a humidistat that lets you set a target RH. For small rooms, a 20 to 30 pint unit works. For larger rooms, 50 pints or more. Desiccant models work better in cool temperatures.
- Humidifier: A cool mist ultrasonic or evaporative humidifier with a humidistat. Avoid warm mist if the room gets above 75°F.
- Fan: A small oscillating fan moving air across the buds, not directly on them. Indirect airflow prevents mold without drying too fast.
- Thermometer: Humidity and temperature work together. Keep the room at 60 to 70°F.
Parameter Bands for Drying Cannabis
These are the ranges that keep drying slow and safe.
how to control humidity during cannabis drying
- Relative humidity: 45 to 55 percent. Below 40 percent, buds dry too fast and lose terpenes. Above 60 percent, mold and mildew grow.
- Temperature: 60 to 70°F. Higher temperatures evaporate terpenes. Lower temperatures slow drying but can increase mold risk if humidity is high.
- Duration: 7 to 14 days. The goal is a slow dry. If buds are dry in 3 days, humidity was too low.
- Airflow: Gentle and indirect. Direct fan on buds causes uneven drying and crispy edges.
- Light: Total darkness. Light degrades THC and terpenes.
Common Pitfalls
- Trusting a cheap analog hygrometer. They are often off by 10 percent or more.
- Setting a dehumidifier to continuous run. It will pull humidity below 40 percent.
- Hanging plants in a room with no air movement. Still air invites mold.
- Using a humidifier with tap water. It leaves mineral dust on buds. Use distilled water.
- Checking humidity once a day. It changes with temperature swings. Use a monitor with alerts.
FAQ
Can I dry cannabis at 60 percent humidity?
No. At 60 percent RH, mold and mildew grow on dense buds. Stay at 55 percent or below.
cannabis drying humidity settings
What if my room is naturally at 35 percent humidity?
Add a humidifier with a humidistat. Set it to 50 percent. Without one, buds dry in 3 to 4 days and smell like hay.
Do I need a dehumidifier and a humidifier?
Only if your climate swings. In most homes, one or the other is enough. Buy the one that matches your typical conditions.
How do I measure humidity inside a jar?
Use a small hygrometer designed for jars. After drying, buds should stabilize at 58 to 62 percent RH in the jar. If it reads higher, burp the jars. If lower, you dried too long.