After an ice storm, I found the rear, drivers side cushion and the carpet
under the cushion and the area around the hatch, sopping wet.  I did notice
that the rear hatch had not completely caught so it was loose and the ice
kept the hatch open and when it melted it came in.  I let it all dry and kept
a watch on it and have not had any more problems.
 It might be that the hatch did not catch and was loose enough to allow the
water to leak in.  Clean and grease the hatch catch and keep a check on it.