I'm guessing this is related to the relative angle of the sun, rather than the sun's actual intensity or how many days it shines. Holland sun most likely hits the bike at a slightly different angle to Florida sun. The problem could also be exacerbated by air-borne particulates which may either filter or refract the sun's rays. The particulate composition of Holland air would be different to that of Florida air.
Then again, maybe I'm just talking out my blow hole.