In the Northern Hemisphere, why are the south-facing sides of buildings often warmer and drier than the north-facing sides?
Well, if you are taking those measurements here and now, think about the season we are currently in in the northern hemisphere. We still have about 2 weeks, give or take, of winter still left. At this time of the year , the northern hemisphere is pointing away from the sun, which means it is receiving less direct radiation from the sun, which directly translates to less temperature, which is what produces winter. Also, the southern side of buildings is what the sun will be radiating upon, so they receive most of that radiation, which will directly translate into warmer southern sides and less moisture than that of the northern sides of the buildings. So take into consideration the seasons, the position of the Earth and the northern hemisphere at that particular time of Earths trek around the sun, which makes up our calendar year.