Lacus Aestatis (latin for "Summer Lake") consists of two relatively small areas of lunar mare located near the western limb of the Moon. The selenograpic coordinates of this feature are 15.0° S, 69.0° W, and it lies within a diameter of 90 km. The lake has a combined surface area in the order of 1,000 km2.
The northwestern part of this feature is located to the east-southeast of the crater Rocca, and is contained within the rim of the satellite crater Rocca A. The other part lies to the southeast of the first, and forms an elongated, irregular patch that extends generally in a north-south direction. The southern tip lies about one crater diameter to the northwest of the flooded crater Crüger.