The average annual rainfall increases from east to west , and it ranges from 700 to 1600 annual millimetres ( 27.6 -- 63 in ) on average , reaching on Mount Pico , the highest Portuguese mountain at .
The average annual rainfall increases from east to west , and it ranges from 700 to 1600 annual millimetres ( 27.6 -- 63 in ) on average , reaching 6300 mm on Mount Pico .