This week, it’s officially time to say goodbye to summer and hello to fall. A lemonade-themed festival and Beer Week barhopping early in the week feel distinctly summery, but by week’s end you can start prepping for Halloween at Universal Studio’s annual fright fest. And as always, check Groupon for even more great things to do in Los Angeles. 2014 US Sumo Open Long Beach | Saturday, September 20 This year's field of 40 challengers includes Byamba, a World Sumo Champion who has taken the title the last seven years in a row. Watch him continue his streak or get upset while sipping Sapporo and Hakutsuru sake. (Walter Pyramid; $25–$70; email to inquire about ringside seats; buy tickets here) L.A. Loves Alex's Lemonade Westwood | Saturday, September 20 Yes, it's pricey, but it's for a good cause: this ongoing food-and-drink event raises money for Alex's Lemonade Stand for Childhood Cancer. And you'll be getting a lot of bang for your buck, thanks to treats and appearances from celebrity chefs such as Giada De Laurentiis and Roy Choi. (Royce Quad at UCLA; $195–$5,000; buy tickets here) Interpol Pomona | Tuesday, September 23 Textured instrumentation and Paul Banks's austere vocals make Interpol's music perfect for ringing in the fall season; just ask fanboy David Letterman, who kept saying he wanted to join the band after their performance of new single ''All the Rage Back Home'' on his show earlier this month. (The Fox Theater Pomona; $32.50–$42.50; buy tickets here) LA Beer Week Various Locations | Saturday, September 20, to Sunday, September 28 If you weren't one of the lucky ones to score a ticket to the sold-out kickoff party, never fear: there are plenty of events throughout the week, including rotating beer flights at Mohawk Bend in Echo Park and an 18th anniversary party at Stone Brewing with specialty vintage beers on tap. (Various locations; free; buy tickets here) Halloween Horror Nights Hollywood | Through Sunday, November 2 Have you ever wondered if you could outrun The Walking Dead’s zombies or The Purge's anarchists? Try your luck at Universal Studio's annual Halloween fest, which has 12 new attractions this year. Discounts available for several dates when purchasing tickets online. (Universal Studios; $52–$209; buy tickets here) Images courtesy of USA Sumo, Interpol, and Halloween Horror Nights’ Facebook page