Shelters in France and Spain on Monday overflowed with exhausted locals and holidaymakers forced to flee blazes so massive some were forming their own mini weather systems, as authorities warned a new heatwave was set to descend on parts of the region. The fires tearing through forests in southwest France, around the prized wine-making region of Bordeaux, and in central Spain around the capital Madrid have been some of the worst in decades and have hit at the height of the summer holiday season.