According to the U.S. Census Bureau, the township has a total area of 6.7 square miles (17.3 km2), all land.

Past and present place names include Feasterville-Trevose, Chinquapin, Churchville, Feasterville, Playwicki, Readingville, Siles, Oakford, Trevose, and Langhorne.

19.9% of all households were made up of individuals, and 7.6% had someone living alone who was 65 years of age or older.

Lower Southampton Township lies within the Neshaminy School District.

The average wettest month is July which corresponds with the annual peak in thunderstorm activity.

During the winter months, the average annual extreme minimum air temperature is 1.1 °F (−17.2 °C).

Ice storms and large snowstorms depositing ≥ 12 inches (30 cm) of snow occur once every few years, particularly during nor’easters from December through February.

Other important roads include County Line Road, which begins at PA 532 and heads northwest along the border separating Lower Southampton Township from Philadelphia and Montgomery County; Bustleton Pike, which follows PA 532 in the southern part of the township before splitting to the northwest; Philmont Avenue, which begins at PA 132 and heads southwest through the southern part of the township; Brownsville Road, which begins near PA 132 and heads northeast through the eastern part of the township; and Bristol Road, which runs northwest–southeast through the northern portion of the township, with a gap between PA 532 and PA 213.

[14] The plant hardiness zone is 7a with an average annual extreme minimum air temperature of 1.1 °F (−17.2 °C).

[8] The spring bloom typically begins by April 8 and fall color usually peaks by November 3.