1992 Ciera front doors leaking

Hi all: Recently I've noticed water leaking into the cabin of my 92 Ciera
through both front door openings. The water seems to be entering from the
same point on both front doors, namely along the bottom of the door opening
approx. 2-3 inches forward of the verticle post that separates the back of
the front door from the front of the rear door. The carpet below those
points on each side is getting damp and the moisture sort-of spreads out in
a plume from there under the front seats. The car is in very good condition
and has been well maintained, and the rubber door seals seem to be intact
and soft all the way around each door, so I can't figure out how or where
the water's penetrating. If anyone here has identified and solved a similar
problem, or can suggest a probable cause and solution for problem just
described, I'd surely appreciate hearing about it. Thanks for your replies!