Altdorf has an average of 133.7 days of rain per year and on average receives 1,099 mm (43.3 in) of precipitation. The wettest month is August during which time Altdorf receives an average of 135 mm (5.3 in) of precipitation. During this month there is precipitation for an average of 13.2 days. The month with the most days of precipitation is June, with an average of 14.4, but with only 127 mm (5.0 in) of precipitation. The driest month of the year is February with an average of 66 mm (2.6 in) of precipitation over 13.2 days
