Humidity rises when lights go out.

Running 2 150mm for grofans in1400×650×2000 ..humidity is perfect while light are on but humidity rises to 68-70 gradual when lights go out.. growth seems perfect though.

Happens to everyone bud.

You need a dehumidifier

projectinfo said:

You need a dehumidifier

Click to expand...

Or, a heater!

Relative humidity is dependent on air temperature, too. If the water vapor content stays the same and the temperature drops, the relative humidity increases. If the water vapor content stays the same and the temperature rises, the relative humidity decreases. This is because colder air doesn’t require as much moisture to become saturated as warmer air.

Yep