Like most of Thailand, Bangkok has a tropical wet and dry climate under the Köppen climate classification and is under the influence of the South Asian monsoon system. It experiences hot, rainy and cool seasons, although temperatures are fairly hot year-round, ranging from an average low of 20.8 °C (69.4 °F) in December to an average high of 34.9 °C (94.8 °F) in April. The rainy season begins with the arrival of the southwest monsoon around mid-May. September is the wettest month, with an average rain fall of 344.2 millimetres (13.55 in). The rainy season lasts until October, when the dry and cool northeast monsoon takes over until February. The hot season is generally dry, but also sees occasional summer storms. The surface magnitude of Bangkok'surban heat island has been measured at 2.5 °C (4.5 °F) during the day and 8.0 °C (14 °F) at night. The highest recorded temperature in Bangkok is 40.8 °C (105.4 °F) in May 1983, and the lowest recorded temperature is 9.9 °C (49.8 °F) in January 1955.
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