Simplify the following text for a Grade 12 native English-speaking person.
Original: The average annual precipitation varies between 900 mm to 1,800 mm depending on the metropolitan zone for a citywide average of approximately 1,000 mm .
Simplified: The average annual precipitation ranges from 900 mm in the drier areas to 1,800 mm in wetter areas , with 1,000 mm average over most of the metropolitan area of Cali .