When ever it is too hot, too cold or too sloppy outside to walk, I mall walk. Check with your local indoor mall to see when the doors open to the public. It's often about 1.5 hours before stores open. Bathrooms are open and it is temperature controlled. You'll probably see others walking too!
Our local Spark People team here in Florida does two mall walks a month during the heat of the summer! It's a wonderful time for face to face support and fun!