The way I understand it, dry rot is associated with seasonal moisture conditions. Dry rot results when wood gets wet, rots, then drys over time. So, Spring and Fall, and mabye Summer, would be prime times where the days get warm enough to hold a fair amount of moisture, then get cool enough to 'squeeze out' the moisture onto wood. The wood rots a short while but when the air warms up, the wood and moisture dry up only to have the cycle begin again when it cools.
Wet rot usually have higher humidity conditions on a more constant basis. The wood rots when it's wet and doesn't get the chance to dry out. So over time, the wood rots.
Dry rot is very common in bathrooms. Wet rot is very common in damp basements and crawlspaces. In the bathroom, the moisture comes, gets absorbed by the wood, then dries until the humidity rises and drops again (like the next shower). In damp basements and crawl spaces, w/o proper venting, there's no circulation and no place for excess moisture to go but into the wood.
I hope this helps. My best to ya and hope this helps.