Is 60/60 Really the Best Way to Dry Cannabis?

Why

Sixty-sixty means 60 degrees Fahrenheit and 60 percent relative humidity. Water activity measures how available the flower’s moisture is to microbes. Given enough time at a stable temperature, flower exposed to 60 percent RH tends toward a water activity of 0.60, within ASTM’s 0.55 to 0.65 range for finished dry flower. But a wet bud isn’t there just because the room reads 60.

Move to 65 degrees and 55 percent humidity? That can work too. With similar airflow and flower, the warmer air and lower relative humidity generally pull moisture out faster than 60/60. Check sooner. Given enough time at 55 percent humidity, the flower tends toward a drier finish. Raise the humidity instead? Water leaves more slowly and damp pockets can linger.

Here’s an actual study outcome: in 2024, researchers dried cannabis in a specialized low-humidity, controlled-gas chamber in about six days while retaining total measured terpenes. During the longer conventional dry, flowers from one variety developed visible mold. Those setups changed more than the number of days. They do not tell us whether 60/60 or 65/55 wins at home. They do show that dragging out the dry isn’t a safety guarantee.

So pick a setting you can hold steady and watch the flower. Damp pockets? Spread the branches and control humidity. Brittle outside? Remove direct fan blast and check the heat and humidity.

Before storage, test representative dense flowers. A calibrated water activity meter measures the finished product. At home, put a sample from your densest flowers in a sealed jar with a hygrometer. Keep it at a steady temperature until the reading stops changing; that can take several hours. Check it again later. If it still reads above about 65 percent, hold off on storage. Test another dense sample, and dry further if the readings stay high. A home hygrometer is a screen, not a mold test.