I'd guess that your air conditioner hose is loose or plugged. Look up under the passenger dash and you'll see a drain hose that can get knocked loose by really big feet. If it's hanging just plug it back in. Otherwise it may be plugged and backing up which will take more fiddling I'd guess.

Haven't had a plugged hose problem so never looking into what's involved there. Usually it's just a loose hose problem.