Fixed by finally replacing the basement window well cover and cleaning he gutters. Yeah!
Went to the basement last week and there was a box that was wet.
O.k. Top of box is dry. No signs of wet insulation above box anyway. Box is old kitchen stuff that shouldn't have any liquid in it. We cleaned out the box. No liquids in it. Looks like the box … on wood, but middle sagged and was on the floor, wicked up water from the floor. Looks like the basement window leaked.
Rained previously and noticed that the gutter on that side of the house was clogged and water was overflowing the gutter.
Heavy rain again and went to the basement. Window well half-full of water and water streaming down the wall.
Cleaned it up.
There was a window well cover over that window when we moved here 16 years ago. Finally dried and cracked apart, and I never replaced it.
Cleaned the gutters with the gutter-cleaning attachment on my blower/vacuum and replaced the cover.
Very heavy rain last night. Basement is dry. Yeah!