A heap can receive rain and still remain dry inside, particularly when leaves or other materials shed water or form a crust. Inspect beneath the outer layer.
Moisten while mixing
If the contents are dry, add water gradually as you turn or mix, so it reaches different layers. Use suitable protection and avoid inhaling dust from very dry material. The target is an evenly moist, aerated mixture rather than a soggy base with a dry top.
Break up large clumps and consider whether the material mix is dominated by dry browns. Suitable greens may help balance the ingredients, but adding a large wet mass in one place can create the opposite problem.
Reduce repeated drying
Review the bin's exposure and cover. A very windy or hot position can make moisture harder to maintain. Follow the design's ventilation needs while reducing unnecessary water loss.
Dryness slows decomposition, but low activity can have other causes, including small volume, cold conditions, or resistant materials. Correct what you observe rather than assuming every cool heap needs more water. Check again after the moisture has distributed, and keep the change modest enough that you can see whether it helped without creating a new saturated problem at the bottom.
Further guidance & source notes
These are background resources, not an endorsement of this website. Regional instructions and the needs of your plant take priority.