Porto Velho features a tropical monsoon
climate (climate type Am) under
the Köppen climate classification. The city features a short dry season that
covers the months of June and July and a lengthy rainy season that covers the
remaining ten months. September is also a relatively drier month, almost giving
the city the appearance of having two separate wet seasons. However September
is not quite a dry season month, seeing on average more than 60 mm of rain.
Porto Velho is particularly wet from December through March, averaging roughly
300 mm of rain
