It's hard to say, but I personally wouldn't rule out the possibility of a leak because you said once it was raining, and another time you were running the air conditioner. Whether it's rain or condensation from the roof air conditioner, it's possible water is getting in somehow.
I would personally inspect the roof area at the front, and then use a hose to shower water on roof for a while. A slow leak may take a while to work its way down to windshield so I'd take my time. Wet roofs can be very slippery and hence dangerous, so it may be best to let someone else you trust check it. This may be a job for dealer if you trust them.
If water doesn't get in, I'd then shower water from hose around the top of windshield.
If everything stays dry, then I'd start looking for sources of excessive humidity and ways to control it.
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