yes old leaves that are dried out, than becomes smashed into a mulch.a way you can check on a toyota is to pull back the carpeting on the passenger side and look for the evaporator drain hose, if the hose is pinched or clogged and you pull it off all the water will go into the passenger compartment so check on the outside under the hood where the hose exits first and see if it is pinched, I have actually seen this, it may also be clogged on the inside, if you pull the hose off the evaporator on the inside and nothing comes out the evaporator drain is clogged, this may be due to small leaves etc that entered through the air vents, in that case poke part of a coathanger in and try to dislodge the objects and try to catch the water with a container.
