Castelnau-Magnoac (French pronunciation: [kastɛlno maɲɔak]; Occitan: Castèthnau de Manhoac) is a commune in the Hautes-Pyrénées department in south-western France.

The average annual temperature in Castelnau-Magnoac is 12.7 °C (54.9 °F).

The average annual rainfall is 876.6 mm (34.51 in) with May as the wettest month.

The temperatures are highest on average in August, at around 20.6 °C (69.1 °F), and lowest in January, at around 5.4 °C (41.7 °F).

This Hautes-Pyrénées geographical article is a stub.