The following day after painting the siding on a house, I noticed wrinkles in various areas of the finish. What went wrong?

When paint is applied in excess of the recommended wet film thickness or when two coats of paint are applied too quick. This will not allow sufficient drying and wrinkling may occur. This surface imperfection should be corrected once the paint film has dried by power sanding. The smooth area should then be primed with a quality oil or latex primer prior to topcoating.