This is NOT a warranty claim. Fog in the lamps is normal - if the water beads up and rolls down the inside of the lens, then they will replace it under warranty. The headlamps and taillamps are not sealed anymore, so the fog is normal.
There is a longer explanation in the owner's manual, but here's a brief excerpt from the FAQ section:
HEADLAMPS - FREQUENTLY
ASKED QUESTIONS
Why is there condensation in the
headlamps?
Headlamps have vents to
accommodate normal changes in air
pressure. Condensation can be a
natural by-product of this design.
When moist air enters the lamp
assembly through the vents, there is a
possibility that condensation can
occur when the temperature is cold.
When normal condensation occurs, a
fine mist can form on the interior of the
lens. The fine mist eventually clears
and exits through the vents during
normal operation.