the mountains receive between 1,000 to 1,500 mm (39 to 59 in) of...

the mountains receive between 1,000 to 1,500 mm (39 to 59 in) of precipitation a year, although some places receive up to 2,500 mm (98 in) of precipitation annually owing to orographic precipitation.[8][9]

by comparison, Melbourne (Australia) average rainfall is around 650 mm a year.

the difference is partly due to the slopes of the Andes forcing the moist, easterly winds to rise, provoking very high condensation leading to the formation of clouds that generate copious amounts of rain.[8]

in conclusion, take it easy waterboy.