I’m not a meterologist. Recall that conditions usually are cold front overriding a warm moist front causing the warm moist air to rise in blocks of air or columns. Then there needs to be wind or frontal movement to start these moist column to start to spin. thenthe updraft feeds more air moving up, causing more spin etc. Geographically, tornados can happen most places and almost any time of year. In fact in Northern Illinois there was a destructive tornado that blew a freight train off the tracks, two weeks ago during a very warm front coming through (today its minus 10) Tornado alley is in OK, TX, KS because warm moist air from the Gulf of Mexico is hit by cool fronts dropping down from Canada or dropping over the Rockies.