- Southern Terminus:
- East Moriches-Riverhead Road (CR 51) and Center Drive South (CR 51) in Riverhead
- Northern Terminus:
- Main Street (NY 25) in Riverhead
Lake Avenue splits off from East Moriches-Riverhead Road (CR 51) as it comes into Riverhead. It runs northeast to a traffic circle at Center Drive (NY 24/CR 94), Flanders Road (NY 24), and Riverleigh Avenue (CR 104). There, it changes names to become Peconic Avenue, which crosses a bridge over the Peconic River to end at Main Street (NY 25). The entire length is a two-lane undivided road.