Just an interesting first person anecdote: In the south of Brazil (close to Argentina) we normally have well defined seasons, but almost like clockwork we always had a famous "mini-summer of May", an unusually warm week in an otherwise cold mid-autumn. Well in the last decade the new concepts of "mini-summer of June" and now "mini-summer of July" started entering the popular parlance, as this abnormally warm weeks during a cold season are becoming more numerous and coming later in the season (late Autumn and even Winter).