Welcome to our forum.
you can try like a an airconditioner seal from homedepot for a temporary fix...http://www.homedepot.com/p/Frost-King-E-O-1-1-4-in-x-42-in-Polyurethane-Air-Conditioner-Weather-Seal-with-15-in-x-24-in-Filter-FAC3/202844547
..... being heavy, indicates it's absorbed a fair amount of moisture, and this will greatly reduce it's insulating ability.
So the cover is larger than the hot tub? If so, leave it alone! It's fine. Doesn't make a difference if it's bigger than the hot tub.However, being heavy, indicates it's absorbed a fair amount of moisture, and this will greatly reduce it's insulating ability.
You should be just fine. Do you have hold down straps on the cover? These will (hopefully) prevent the wind from pulling the top off.
Terry, Buy a set of these. They are extremely easy to install. http://www.spadepot.com/shop/Sure-Lock-Spa-Cover-Locks---Set-of-4-P4499C1.aspx