Lake Welch Beach is the main public swimming beach in Harriman State Park, a half-mile strip of sand on the eastern end of 216-acre Lake Welch in the Town of Stony Point, Rockland County. New York State Parks runs it together with the Palisades Interstate Park Commission. The lake is man-made: the commission dammed swampy Beaver Pond and flooded the small settlement of Sandyfield to create it, and the work was finished in the early 1940s. It is the largest beach in Harriman, backed by wooded ridges of the Ramapo Mountains.

The park address is 800 Kanawauke Road, Stony Point. Most drivers come in on Lake Welch Drive (the old Lake Welch Parkway), which leaves the Palisades Interstate Parkway and runs southwest past the beach entrance toward Seven Lakes Drive. Kanawauke Road (County Route 106) crosses the lake to the west and gives the classic view back toward the sand. Large paved lots sit just behind the beach, and a short walk through lawns and picnic groves puts you on the sand. On hot summer weekends the lots can fill, so arriving early matters.

The beach is soft sand and the bottom stays sandy as you wade in. Buoy lines mark the swim zones, and a row of numbered lifeguard chairs runs the length of the shoreline. Swimming is allowed only inside the marked areas while lifeguards are on duty. Swimming typically opens on weekends and holidays in late May and runs daily from late June through Labor Day, with posted swim hours in recent seasons of 10:00am to 5:45pm on weekdays and 9:00am to 6:45pm on weekends and holidays. After Labor Day the beach switches to picnicking only, with no swimming or wading. There is no current to deal with, and the lake water is noticeably cooler in early June than by late July.

Lake Welch is not free in summer. A $10 per car vehicle use fee (cash or credit) is charged on weekends and holidays from late May to mid-June, and daily from about June 20 through Labor Day; there is no entrance fee the rest of the year. From mid-October to late April the area is open Monday through Friday, 8:00am to 4:00pm, for picnicking only (gates close at 3:30pm) and is closed on weekends and holidays. Pets are not allowed anywhere at Lake Welch between Memorial Day weekend and Labor Day, alcohol is banned, and from October to April there is no running water, only a portable toilet.

The main hazard here is harmful algal blooms. A lakewide blue-green algae bloom kept the beach closed for most of summer 2022, and another bloom closed it for about a week in July 2024 until park staff treated the water with algaecide and tests came back clean. State Parks now runs monitoring buoys in the lake that pick up rising algae pigments before a bloom is visible. Check the State Parks page or app for swim status before you drive out, stay out of water that looks green, scummy or discolored, and rinse off if you have been in it during a bloom.

Beyond the beach there are shaded picnic areas with grills, a food concession, fishing and a boat launch, and in winter the lake is used for ice fishing and skating. Hiking trails such as the Beech Trail run through the woods north and west of the lake. Beaver Pond Campground adjoins the recreation area just southeast of the beach for anyone who wants to stay overnight.