Many thanks to everybody, esp. Ron and John for the follow up inquiries. Our driveway is a blacktop with sufficient slope. I believe the problem is the lip section of the concrete garage floor, an area of approx.one foot between the garage door and the blacktop driveway, where the grading is somewhat insufficient. It seems that the rain water, falling down to this area, and also dripping down from the garage door, does not properly flow away from this area into the driveway. It seeps into the garage.