It has an average altitude of above sea level with most of the surface flat. The territory is mostly the bed of the former Lake Texcoco with soils of compressed clay over sand, with the exception of the Peñón de los Baños at above sea level, made of basalt . Because it is mostly former lakebed, flooding (especially during the rainy season from June to October) and hailstorms in winter, are not uncommon. Flooding is often caused or exacerbated by the deteriorated drainage system. Aside from the one elevation, the far west of the borough corresponds to the far east of the former Tenochtitlan island. For this reason, about one quarter of the historic center of Mexico City belongs to the borough. It has a semi dry, temperate climate with an average annual temperature of and an average rainfall of .