How to avoid problems when filming in a bath house I'm going to cover a concert early June inside a bath house. I've visited the location and it's both quite hot and humid. The plan is to bring in at least three video cameras and have them running constantly for an hour or so (there will be a Panasonic GH2, a Canon  HF10, and probably some fairly cheap sony video camera). I will also use a couple of self-powered michrophones (such as the zoom H1).

External power is of course something I will have to abandon, but are there any other tips what I should think of to keep this event safe and high-quality? What kind of problems can I expect to run into?
Get underwater housings for your cameras. Since it doesn't sound like you will actually be dunking the gear under the water, you can probably get away with the cheap bag-type housings.

To avoid fogging up the lenses, let your gear warm up to the ambient temperature, then clean the lens.