Older USGS topographic maps show the township in a region known as the Mahoning Hills, a geologically chaotic series of hilltops surmounting a long upland more cyclic in altitude than nearby valley bottoms.

The southern boundary of the township follows the crest of Blue Mountain, a prominent ridge that runs across the eastern half of the state and reaches an elevation of 1,680 feet (510 m) in this area.

The northern boundary runs near the broader and lower crest of Mahoning Mountain, elevation 1,150 feet (350 m).

Villages in the township include Ashfield, Germans, and West Bowmans.

[3] East Penn has a humid continental climate (Dfa/Dfb) and the hardiness zone is mainly 6a with 6b along the river and in the Lizard Valley along 895.

Average monthly temperatures in Ashfield range from 27.6 °F in January to 72.4 °F in July.

Local access to the township is provided by Pennsylvania Route 895, which crosses the township from southwest to northeast after crossing the southern tier of Schuylkill County and ends at an interchange with Pennsylvania Route 248 across the Lehigh River in Bowmanstown.