Most likely a bad seal, or a crack have you ever removed the headlights or popped open any of the openings? If so go back and check the seals

As far as the moisture you will want to open the openings and either use a hair dryer or turn on the high beams on a hot day, it takes some time to fully dry the headlight as it may appear its dried once you hit it with the dryer but later you will find out the moisture gets drawn out from else where in the headlight.

 

 

Thanks everyone for your help. Where's the low beam leveler btw?

 

In my old Volvos I had this problem, easy solution to dry. Opened up the back end by removing the "bulb" and allowed it to air dry. After 1 day of driving around with the opened back, the moisture would disappear. The problem now is how to seal tight, this will take some doing.

 

i don't think any headlight from any brand is completely air tight. It is intentional to let air in and out.
Moisture is always in the air, so if it were air tight with atmospheric air inside, under the right temperature, it would still have condensation.
You have no way to make a vacuum inside.

I would blow out all the water with a fan. Don't let the water droplets dry out on the lens, or they may leave water marks..