This happened to the lights on my Porsche and many many other owners. Depending on how the lights are designed it may be completely normal. Here is what Porsche says about theirs:
The following lighting components:
- Headlights
- Side direction indicator light
- Front direction indicator light
- Fog lights
- Auxiliary headlights
- License plate light
- Tail light
- Additional brake light
Concern:
Customers complain that lighting components are fogged up.
Particularly at cold outside temperatures and/or when air humidity is high, moisture can build up on the inside of the lens.
Lighting components are
not designed to be completely leak-tight due to the open, spray water-proof ventilation system (required for pressure compensation purposes).
A build-up of moisture on lighting components is not caused by a defect and does not reduce the light output in any way. For this reason, if lighting components fog up, this is
not a safety-relevant complaint and
does not necessarily justify replacement of the affected lighting components.