With the dog days of summer over, September means it’s time to fold up the seersucker suit, put away the window air conditioning unit and venture outside again.

Luckily for Washingtonians starving for some fresh air, the 10th annual WalkingTownDC event kicks off this weekend, with more than 120 guided walking and biking tours spanning Saturday and Sunday.

Organized by Cultural Tourism DC, a nonprofit coalition of arts, cultural and heritage organizations dedicated to increasing awareness of tourism in the District, the event features tours of both familiar and off-the-beaten-path sites, from monuments and Civil War battlefields to local neighborhoods and forgotten cemeteries. Other tours are also arranged thematically, focusing on nature, architecture, politics or military history.

According to Courtney MacGregor, a spokeswoman for Cultural Tourism DC, the organization works hard “to promote D.C. beyond the National Mall.—

“The walking tour is definitely a local event,— she added. “It’s mostly people who are looking to explore their own backyard.— This year’s event is expected to draw as many as 3,500 participants, while past years have drawn as many as 4,000 people — most from D.C., Virginia and Maryland.

Staffers stuck at the office this weekend may also see groups around the Capitol grounds, with at least nine tours scheduled for the Capitol Hill area. The “American Symbols— and “In the Shadow of the Dome— tours take participants to more conventional sites like the Mall, the Supreme Court and the Library of Congress, while less traditional tours like “Tree Walk— — focusing on the oaks and elms of Capitol Hill — explore the quirkier sides of the neighborhood.

Other Hill tours include “Gay and Lesbian Capitol Hill,— a tour of lesbian, gay, bisexual and transgender cultural landmarks along Pennsylvania Avenue, and “If This Street Could Talk,— a five-block stroll down the Eighth Street Southeast corridor to the Navy Yard.

There are several tours for bicycle enthusiasts as well, including a night tour of D.C.’s famous monuments, a 25-mile scenic loop of Ward 5 in Northeast D.C. and a ride along the rapidly developing waterfront of the Anacostia River.

The weekend of walking and biking tours also culminates in Car Free Day, an international event promoting awareness of alternative means of transportation, celebrated on Tuesday, Sept. 22. Cultural Tourism DC decided to link WalkingTownDC with Car Free Day this year because the two events seemed like natural companions.

“Because WalkingTownDC has a walking component, we thought there’s a natural link to Car Free Day,— MacGregor said.

All tours are free, but about half require advanced online reservations. Guides are a mix of professional D.C. tour guides and amateur local experts, all of whom have donated their time to the event. WalkingTownDC is also soliciting volunteers to help with the logistical elements, quality control and participant feedback.

Visit walkingtowndc.com or call Cultural Tourism DC at 202-661-7581 for the complete schedule of walking tours and volunteer opportunities. For more information on Car Free Day events, visit carfreemetrodc.com.