Protected by the Titiwangsa Mountains in the east and Indonesia’s Sumatra Island in the west, Kuala Lumpur has a year-round equatorial climate which is warm and sunny, along with abundant rainfall, especially during the southwest monsoon season from September to April. Temperatures tend to remain constant. Maximums hover between 31 °C and 33 °C (88-92 °F) and have never exceeded 37 °C (99 °F), while minimums hover between 22 °C and 23.5 °C (71-74 °F) and have never fallen below 19 °C (66 °F). Kuala Lumpur typically receives 2,266 mm (89.2 in) of rain annually; June and July are relatively dry, but even then rainfall typically exceeds 125 mm (5 in) per month.

Flooding is a frequent occurrence in Kuala Lumpur whenever there is a heavy downpour, especially in the city centre and downstream areas. Dust particles from forest fires from nearby Sumatra sometimes cast a haze over the region. It is a major source of pollution in the city together with open burning, emission from motor vehicles and construction work.