Having issues with my childs clothes.?

My 16 month old is in a size 18 months in shirts...but the pants are too big around his waist and too short on his legs (they look like steve urkel pants lol). Size 12 months are too small, and 24 months are waaaay to big on his waist. Any other parents having this problem? It's starting to get cold here and I can't have him in short pants, but i can't have his pants falling off of him either. What can I do?