CLIMATE & WEATHER

Bangladesh has a tropical monsoon climate characterized by rain bearing winds, moderately warm temperatures and high humidity. Winter is mild, dry and sunny with average daily temperatures ranging between 50-80 degree F (10-27 degree C). January is the coolest month in the winter season which lasts from November to February. During winter, the eastern half of the country receives an average of less than 7 inches (180 mm)of rain, and the northwest receives less than 3 inches (75 mm).

April and May, the season of little rains, that are important to farmers waiting to plow their fields for an early crop, bring more than 150 inches (380 mm) of rain to the eastern half of the country. This is the hottest season of the country with an average daily maximum temperature of around 90 degree F(32 degree C) and a minimum temperature of 70 degree F (21 degree C). The rainy season properly extends from June to October when the monsoon air stream sweeps in from the Bay of Bengal. During this time, Bangladesh receives heavy rainfall. Except for some parts in the west, it generally exceeds 60 inches (1500 mm) annually. Large area of the south, southeast, north and northeast receive 80-100 inches, and northern and northwestern part of Sylhet area receive 150-200 inches. Although temperature do not exceed the high 80's on most days during the season, they vary only slightly and may fall by only 10 degree F at night. The rainfall in April, September and October is crucial to the farmers. Without April showers to soften the ground, farmers may have to delay sowing the early rice crop - Aus, and major cash crop - jute. The little rains are erratic in an incidence and variable in quantity with consequent uncertainty for agricultural production. Failure of the late rains can seriously reduce the main crop - rice.

The condition of lowest atmospheric pressure occur in June and July. Winds are mostly from the north and the northeast in winter, blowing at a rate of 1-2 miles per hour in the northern and central areas and 2-4 miles per hour near the coast. During the period of northwesters (March - May), wind speed rises to 30-40 miles per hour.

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.

Storm warning signals in Bangladesh

Storms generally occur in Bangladesh in the months of April-May and October-November (early part). The Meterological Department uses different codes of signals for storm warnings at maritime and river ports. These codes are given below in abbreviated forms.

It should be noted that the signal numbers in the two codes do not carry the same significance and, in particular, that higher signal numbers within the danger and great danger maritime groups indicate differences in storm location, not difference in storm intensity.