Why does weather change so fast over night? One day it was gorgeous an at night slightly warm an than the next morning there's snow. Why?

Just the way it goes this time of year, well depending on where you live.
But up around the 45 degree latitude, weather this time of the year can be a bit odd.
Rain, snow, sunshine and we had hail here the other day. A hail storm followed by temperatures in the 50s and sunshine.
I guess it beats being bored with the weather.