Shannon Beach, officially the Senator Charles E. Shannon Jr. Memorial Beach, is the public swimming beach of Mystic Lakes State Park, run by the Massachusetts Department of Conservation and Recreation (DCR). It sits on the north shore of Upper Mystic Lake in Winchester, close to the Medford and Arlington lines, and DCR lists the park under a Medford mailing address, 481 Mystic Valley Parkway. Older locals still call it Sandy Beach, its name until the state renamed it in 2008 for Charles Shannon, who represented Winchester, Medford and Somerville in the state Senate from 1991 until he died in 2005.

The beach is right off the Mystic Valley Parkway just south of Wedgemere. Parking is free, but the lot is small and fills early on hot weekends, and parking on the parkway shoulders is not allowed and can get you towed. The easiest way in without a car is the Lowell Line commuter rail to Wedgemere station, about a ten minute walk away. The park is open sunrise to sunset, and there is no entrance or parking fee.

The beach itself is a short strip of sand in a small, tree-lined cove that opens onto the lake. Swimming is limited to the roped area in front of the sand. In 2024 DCR staffed lifeguards on weekends and holidays from late May to mid-June, then daily until mid-August, and closed the swim area for the year in early September; check the current year's schedule, since the dates shift. A net-zero bathhouse opened in 2023 with restrooms, a family restroom and outdoor rinse showers, and DCR keeps a beach wheelchair here, with accessible paths from parking to the sand and the picnic grove.

Water quality is the main issue at Shannon Beach. The Aberjona River and stormwater drain into the north end of the lake, and the beach has been closed for high bacteria at some point in each of the last several summers, often in the day or two after heavy rain. It was closed during the late June and early July 2026 heat wave after enterococci samples ran far over the state limit, including one reading of 2,419.6 CFU per 100 mL on June 16, and DCR shut it in July 2017 for a cyanobacteria bloom. On closure days DCR hangs red flags on the lifeguard chairs and pulls the guards. Before you go, check DCR Park Alerts and the state Department of Public Health beach water quality dashboard, and stay out of the water when it's posted, even if other people are swimming.

Drowning is the other real risk. People have drowned at the Mystic Lakes in July of 2019, 2022 and 2023. In the 2023 case a 17-year-old was swimming with a group about 100 yards offshore, well outside the roped swim zone, on a day the beach was already closed for bacteria, and he was found in about six feet of water. Stay inside the ropes and don't swim when no lifeguard is on duty. As of October the swim season is over and no guards are posted until next summer.

Around the beach there is a large grass field, a playground, a shaded picnic grove and walking paths along the shore. Gas and propane grills are allowed but charcoal is not, alcohol is banned, and dogs are not allowed on the beach from April 1 to September 15. Upper Mystic Lake is open to non-motorized boats, and people paddleboard and kayak from here; sailing programs run out of the Tufts University boathouse farther down the lake.