AC condensation in cabin?

[elchivito]

Sonny boy reports that he's noticed a very cold drip coming in the passenger side footwell, up near the firewall. I checked the carpeting this morning before he left and it wasn't wet, so I'm thinking it's not a lot. I'm assuming it's AC condensation as it's cold. The AC works very well, gets nice and cold, even for AZ 100+ temps. Any ideas how to track this down. BTW, it has been extremely dry here, single digit humidity for weeks. Thanks!