Used as a conjunction, they are synonymous and can be used interchangeably. "Though" can also be used as an adverb to mean "however." Although cannot be used in this case.

though (conjunction) despite the fact that (synonym although) Anne was fond of Tim, though he often annoyed her. Though she gave no sign, I was sure she had seen me. His clothes, though old and worn, looked clean and of good quality. Strange though it may sound, I was pleased it was over. (2) used to add a fact or an opinion that makes the previous statement less strong or less important They're very different, though they did seem to get on well when they met. He'll probably say no, though it's worth asking. although (conjunction) used for introducing a statement that makes the main statement in a sentence seem surprising (synonym though) Although the sun was shining, it wasn't very warm. Although small, the kitchen is well designed. (2) used to mean ‘but’ or ‘however’ when you are commenting on a statement I felt he was wrong, although I didn't say so at the time.