Photo by bossa67.

HAPPY HOUR: The D.C. Chapter of the Sierra Club is hosting a happy hour and streetcar discussion at SOVA espresso and wine bar (1359 H Street NE) tonight. 6 p.m.

MUSIC: Lou Barlow (of Dinosaur Jr. and Sebadoh fame) comes to the Rock and Roll Hotel (1353 H Street NE) tonight. Wye Oak also performs. $12/$14, 8:30 p.m.

FITNESS: Head to the Liaison Hotel (415 New Jersey Avenue NW) for the Step Out, Jump In! rooftop pool party event to fight diabetes. Update: Oops, this event was yesterday, apologies.

FAIR: The Arlington County Fair kicks off tonight at the Thomas Jefferson Community Center (3501 South Second St. Arlington). Besides riding rides and eating delicious fried things, check out Bixby’s Rainforest Rescue’s showcase of exotic animals (a sloth, birds, and snakes) while you learn about rainforest conservation at 6:30 and 8 p.m. The fair runs through this Sunday, and will feature other events (like piglet racing!) throughout the week. Find more information and updates on the Fair’s Facebook wall. 5-10 p.m.