There was another rumble of thunder outside, and then the sky started to unload on what poor ponies hadn't made it to shelter in time. Usually Canterlot only got scheduled drizzle during the daytime, with major showers reserved for the night; this must've been a big weather pattern if the Airborne Weather And Climate Service pegasi couldn't break up the storm front without putting it in the forecast. It was pretty rare for severe weather to slip by the AWACS.