Each year, 54 mikoshi teams together with dancers and musicians parade the streets of Koto-ku. In total, 30,000 people participate in the parade. A crowd of 500,000 cheers them on (and throws water at them). It's thought that the gods (in the mikoshi) enjoy a good summer soaking.
The water soaking also has a practical purpose. Mikoshi weight thousands of kilograms and Tokyo summers are often incredibly hot and humid. The mikoshi teams are refreshed by the constant onslaught of cool water.
Teams toss the 2,500 kilogram (5,500 pound) mikoshi into the air as a show of energy and strength.
The Fukagawa Hachiman Festival is held the 3rd weekend in August at Tomioka Hachimangu Shrine in Fukagawa. Every third year the festival is supersized (including 2014, 2017, 2020 …). The supersized version of the festival (Hon-matsuri) is 5 days long.
The festival runs rain or shine.