I have a one room seasonal cottage in Rochester NY. The walls and ceiling
are cedar. The ceiling is attached directly to the roof; there is
insulation and a vapor barrier, but no air space. It is about 15' high at
the peak.
I have been in there a few times, but it hasn't been used since last fall.

Today I got a ladder out to change the smoke detector battery, and noticed
it got very warm and humid as I went up. The smoke detector actually had
water on it, and the top couple feet of the wall (up near the peak) was
wet.

It is right next to the chimney, so the first thing I thought of was that
the flashing was leaking, but I would think that the water would have come
further down the wall and I don't see why the smoke detector would have
water on it.

Instead I figured that there were a few warm humid days followed by some
cold weather. The warm humid air got trapped near the ceiling and condensed
when the roof cooled off.

Does this make any sense, or should I get a roofer out? Any other ideas?
There was a major roof leak before I bought the place, but it was reroofed
and seems to have been fine since.
Thanks.