I wasn't even referring to signs that are only applicable in specific weather conditions, just pointing out the absurd amount of handholding drivers tend to get. Some drunk chump might run straight into the trees? Add more reflective chevrons. Someone still crashed? Add flashing LEDs.

And yes, German signage certainly does weather dependency, speed limits with "Zusatzzeichen 1052-36" are quite frequent (I think it's put up everywhere the surface doesn't drain as good as it should, e.g. if surface angle changes slightly from the ground setting after construction)