Climate

Bangladesh has a typical monsoon climate characterized by rain-bearing winds, moderately warm temperatures, and high humidity. In general, maximum temperatures in the summer months, from April to September, are in the low to mid-90s F (mid-30s C). April is the warmest month in most parts. The range of high temperatures in the winter months, from November to March, is greater than in the summer months. January is the coolest month, with high temperatures averaging in the mid- to upper 70s F (mid-20s C).

The conditions of lowest atmospheric pressure occur in Bangladesh in June and July, the storm season. Winds are mostly from the north and northeast in winter, blowing gently in northern and central areas and somewhat more aggressively near the coast. During the period of the northwesters (strong winds from the northwest) from March to May, however, wind speeds may rise to 40 miles (65 km) per hour.

Bangladesh receives heavy rainfall; except for some parts in the west, it generally exceeds 60 inches (1,500 mm) annually. Large areas of the south, southeast, north, and northeast typically receive from 80 to 100 inches (2,000 to 2,500 mm), and the northern and northwestern parts of the Sylhet area usually receive from 150 to 200 inches (3,800 to 5,000 mm). The maximum rainfall occurs during the monsoon period, from June to September or early October.

Storms of very high intensity often occur early in the summer (in April and May) and late in the monsoon season (September to October, and sometimes November). These disturbances may produce winds with speeds exceeding 100 miles (160 km) per hour, and they may generate waves in the Bay of Bengal that crest as high as 20 feet (6 metres) before crashing with tremendous force onto the coastal areas and the offshore islands, causing heavy losses of life and property. Since the early 18th century, when records were first kept, more than 1,000,000 people have been killed in such storms, some 815,000 of them in just three storms occurring in 1737, 1876, and 1970