it is condensation
Boston is definitely in the north this for every body
It has moisture (water) in it.
NEVER
because they like the extra moisture.
due to action of air and moisture on it
Boston blackie
Along the equator and oceans. It's this combination of moisture and heat that creates hurricanes.
Humidity - water vapor mixed with air - is drawn to the coolest surfaces, like windows. Cool air can't hold as much moisture as warm air so windows often collect this moisture and make it visible.
Like more than ten years ago.
Both "more moist" and "moister" appear to be accepted, though "moister" sounds much like "moisture".
You cannot remove the moisture for the long term as the sealed beam seal has failed and moisture will continue to appear later. Usually a heat gun could be used to heat up the glass, careful not to melt any nearby plastic parts. Best bet is to replace the headlight.