Summer vacation may be over, but September is packed with hot happenings. Marking the start of London's Autumn Season, September has plenty in store, from fabulous festivals to blockbuster exhibitions.

This fall, it's all about the festivals, many of which are free to attend. The Totally Thames Festival is back with a month of river-related fun, including artworks, live performances and boat races. Other Totally Thames Festival highlights include Maria Arceo's Future Dust, a large-scale art installation made from plastic collected along the Thames. The artwork will light up at night and move to different riverside locations.

The Raindance Film Festival is a must for film buffs. It's rolling out the red carpet for 12 days in September, with a packed program of screenings, parties, seminars and workshops.

Travel back to Roman London with Londinium: a season of gripping events and activities including guided walks, a play about the vengeful Boudica at Shakespeare's Globe Theater and more. September also means the return of Daylight Music, a carefully curated series of concerts in the atmospheric surroundings of Union Chapel, to be enjoyed with tea and cake every Saturday afternoon. The eclectic and diverse program changes every week and has included artists such as Alexis Taylor from Hot Chip and Nils Frahm.

For art enthusiasts, this month is buzzing with not-to-be-missed exhibitions. Opening at the Barbican is Basquiat: Boom for Real, the first large-scale UK exhibition for Jean-Michel Basquiat, the pioneering prodigy of downtown New York's art scene in the 1980s. Another must-see is the anticipated exhibition Jasper Johns: Something Resembling Truth at The Royal Academy of Arts. The landmark retrospective features more than 150 works, including iconic images of flags, targets, maps and light bulbs.

See your favorite celebrities on stage in one of London's new West End shows. Sienna Miller and Jack O'Connell sizzle in Tennessee Williams's family drama Cat on a Hot Tin Roof at the Apollo Theatre.

Museum fans are in for a special treat this month with a series of blockbuster exhibitions taking place. Discover the long-hidden Siberian culture at Scythians: Warriors of Ancient Siberia at the British Museum, and explore the unsolved mystery of Sir John Franklin's doomed last voyage into the Arctic at National Maritime Museum's exhibition Death in the Ice.

Catch the last month of Buckingham Palace's Summer Opening and take a peek around 19 lavishly decorated state rooms of the queen's London home. On display at the palace's Queen's Gallery is Canaletto & The Art of Venice, featuring dreamy artworks showing the beauty of 18th-century Venice by Venetian artist Canaletto and his contemporaries. At Diana: Her Fashion Story at Kensington Palace, you can view the Princess's glamorous gowns, including the blue velvet gown she famously wore when she danced with John Travolta at the White House.

Autumn in London is open. Book your London adventure by visiting united.com or through the United app. And while you're there, share your experience on social media with the hashtag #LondonIsOpen and #AutumnSeason.