I don't think this really means anything. If you track the indoor temperature and outdoor temperature at my apartment, they correlate. But it's because I come home as it's getting cool and turn on the AC, and I leave for work before it gets too hot out. So the shape of the graph looks the same, but the relationship is that I come home from work at the same time of day when the sun sets, not that the outdoor temperature affects the indoor temperature. (Weekends are proof, it's cold all day indoors then :)