The London is Open for Summer campaign includes a short video (below) featuring a host of celebrities - including indie band The Kaiser Chiefs - discussing what they love about London during summertime.
#LondonIsOpen was initially launched by the Mayor to demonstrate that London was united and "open for business" following Britain's vote to leave the EU.
The summer reboot follows research by tourist board Visit London that reveals the number of tourists visiting the city is set to increase by 14 per cent between July and October in comparison with the same period last year.
The research also shows that one third of Brits are considering taking a trip or booking an overnight stay in London during the summer.
Khan said: "London is the greatest city on earth and there is nowhere better to spend time this summer. Every corner of the city is bursting with life and colour. I'm saying loud and clear - London is open for business and open to everyone this summer."
The campaign was created by PR firm Freud Communications.