i mean u cant really heavily affect weather unless the MC caused mass pollution even if the butterfly effect is taken into account
even now humans cant intentionally control weather, much less if they aren't actively trying to affect the weather
but yeah the fact that they said the castle was atop a cliff and it somehow flooded is pretty weird
well i guess the castle doesn't have proper drainage system. Or the heavy downpour is some kind of an anomaly, that conveniently happened right when the MC needs it.