The French city of Bordeaux hits its highest temperature since records began with 41.2C (106.1F).
Kleine Brogel in Belgium hits 38.9C (102F) and a Eurostar train breaks down in searing heat.
Weather warnings have been issued across the Continent, with record temperatures expected this week.
She has taken her final PMQs and will later give a speech in Downing Street before making way for her successor.
Johnson has cultivated a reputation as a charming upper-class womaniser, cheat and liar – and Britain loves him for it.