That’s a very interesting question. Unfortunately the data sheet is very vague with no operating humidity range specified, but there is this note,
“12 When inside of the sensor is moisturized, this product does not keep its proper function. Please design the application so that moisturization of the sensor does not happen.”
which could be interpreted as it not really being suitable for outdoor use :?
There are a lot of papers online about the role of particulates in fog formation so it’s also possible you are seeing a real effect.
:dontknow: