Hi,
first of all I have to say my CX-7 is sleeping all nights in the open and it's quite cold since a month or so, around 0° C. On the right rear light I've now some water condense that is persisting since days. I don't know exactly how to remove it: I thought about to try with a hairdryer after having opened it as for substituting a light bulb, but if you have suggestions...
Moreover, is it dangerous for the lights and electric circuits?
What could be the cause since the light set was never changed and it never happened before? The only thing that come into my mind, even if it sounds ridiculous, is that I tend to keep my swimming pool bag on that side of the rear trunk..

Thanks

 

Thats normal. As time goes by, the tail lights varies between hot and cold, it contracts and it sets out. What happens is that the sealant between the outside cover and the inside cover deteriorates after time and water will enter. We normally just take a vacuum cleaner and vacuum the taillight until it becomes dry. (Leaving a hole open on the other side of course so that the air can get pulled through the taillight to dry out. A hairdryer might just damage the plastic) Hope it helps.

 

That's a good suggestion for clearing out the moisture, but moisture in your taillight is not normal. They are a sealed unit, and the bulb sockets should also have a foam or rubber seal around them.
Yes, it will do damage to the electrical circuits in time. I would check there first for leaks.
If that doesn't do it, check for cracks in the lens and/or around the seal between the lens and reflector housing. You will need to remove the entire assembly to accomplish this properly. If an air compressor is available, seal off all but one the light socket holes and apply LIGHT air pressure. 20 psi should do it. If there's a leak, you should be able to clearly tell, and reseal it using this method.