2-5 lightning strikes that sets everything on fire everytime I log onto my server

Every time me or my friends log onto my server about 2-5 lightning strikes happen next to us and set everything around us on fire and spawns skeleton horses. I know the lightning strikes are supposed to happen when skeleton horses spawn but I thought skeleton horses were supposed to be rare? This happens almost every time we log onto the server and it's getting quite annoying having to put out the fires each time and rebuild everything.