According to the records, it had a fairly normal weather pattern when it was first settled. Then, as the population grew and urbanization spread, more energy was used and more heat was discharged into the atmosphere. The ice cover contracted, the cloud layer thickened, and the weather got lousier. That encouraged the movement underground and set off a vicious cycle. The worse the weather got, the more eagerly the land was dug into and the domes built and the weather got still worse. Now the planet has become a world of almost incessant cloudiness and frequent rains - or snows when it's cold enough. The only thing is that no one can work it out properly. No one has worked out an analysis that can explain why the weather has deteriorated quite as it has or how one can reasonably predict the details of its day-to-day changes.

— Prelude to Foundation by Isaac Asimov (Foundation, #6) (Page 110)