Weather

So I walked in this morning in the rain, and got down to work.

As I was pacing the corridors at about 2:30-3 ish (I do this a lot: fortunately nobody on my corridor is around at the moment), I noticed that the weather had cleared right off and made the mental note, once I had upicked the current knotty problem, to nip up to the 2nd floor and take a pic of the view over to the prison.
Next thing I know, I hear the rain on my window. So this is the last bit of that sunny weather before it disappeared under a spectacular rainstorm. Why are we suddenly in the tropics?