Speed limit info accounting for rain

I remember threads where we discussed whether the speed limit info reads the signs or the info is fed through the navigation system and concluded this being a mixture of both. Just discovered it also adjusts the indicated speed limit to the weather conditions, the rain. In some countries, like France or Luxembourg, the speed limit during rain is by law lower which is not indicated by the physical roadsigns, except very occasionally as reminders. I just drove through France on a highway and noted the speed limit is apparently coupled with the rain sensor as it showed me different max speed values on the same sections of the road depending on the rain situation. Interestingly, the wipers do not have to be on, so it works with the sensor rather than actual movement of the wipers.