Castelnau-Magnoac has an oceanic climate (Köppen climate classificationCfb). 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). The highest temperature ever recorded in Castelnau-Magnoac was 39.7 °C (103.5 °F) on 13 August 2003; the coldest temperature ever recorded was −11.8 °C (10.8 °F) on 25 December 2001.
Climate data for Castelnau-Magnoac (1991−2020 normals, extremes 1986−present)