Bangladesh has a tropical monsoon type climate with a hot & rainy summer and a dry winter. January is the coolest month with temperatures averaging near 26 deg C (78 d F) and April the warmest with temperatures from 33 to 36 deg C (91 to 96 deg F).  Most places of Bangladesh receive more than 1,525 mm of rain a year, and areas near the hills receive 5,080 mm ). Most rains occur during the monsoon (June-September) and little in winter (November-February).
The coastal districts of Bangladesh, particularly those flanking the Meghna estuary, are susceptible to serious damage from cyclones, which cause major losses of life and property. In the early summer (April and May) and late in the monsoon season (September to November) storms of very high intensity often occure. They may create winds with speed of 100-150 miles per hour piling up the waters of Bay of Bengal to crests as high as 20 feet that crash with tremendous force onto the coastal areas and offshore islands. Since the early 18th century, when records were first kept, more than one million people have been killed in such storms –815,000 of them in three storm occuring in 1737, 1876 and 1970. Severe storms also occured in May 1985 and April 1991. Lesser hazards in the region are hailstorms, particularly in March and April, and tornadoes.

Bangladesh has warm temperatures throughout the year, with relatively little variation from month to month. January tends to be the coolest month and May the warmest. In Dhaka the average January temperature is about 19°C (about 66°F), and the average May temperature is about 29°C (about 84°F).

Bangladesh is one of the most flood-prone countries in the world. Essentially, it’s the flood plain where two huge rivers–the Ganges and the Brahmaputra–carry spring snowmelt from the towering Himalayan Mountains to the sea. When the rivers flood, so does Bangladesh.

Bangladesh being mostly formed of the Gangetic delta, will be impacted severely if sea-levels rise as a result of the greenhouse effect. Read about the potential impact on bangladesh.