From May to September, moist oceanic air converges over the hot Indian subcontinent and downpours soak crops, overflow rivers, and turn streets into canals.

The word "monsoon," which comes from mausim, the Arabic word for seasons, refers to complex seasonal winds that sweep across Asia and other areas. In winter Asia's monsoon winds are fairly dry. In summer, however, the winds bring drenching rains on which several billion Asians rely.

Farmers, and many economies, depend on the monsoon's timely arrival. Intense rains are necessary for rice and other crops. As rivers overflow banks, water soaks into farmlands, leaving behind nourishing silt and algae as it recedes.

If unusual conditions occur and the monsoons fail to arrive, drought occurs. Hundreds of thousands of deaths from starvation are possible.

Although rainfall amounts vary every year, monsoons provide about 80 percent of India's rainfall, on average. In one record yearlong period, 1860-61, monsoon rains dumped 1,042 inches (2,600 centimeters) of moisture on the Himalaya foothills.

In southern India the Western Ghats mountain chain absorbs most of the monsoon's rains and then releases the water gradually over the rest of the year. As much as 29 feet (9 meters) of rain falls every year in some sections.

In densely populated Bangladesh, floods inundate a fifth of the country every year. Many people make homes on chars, small, temporary islands in rivers. During the flood season, when cyclones add to monsoon rains, most chars rise only 1 foot (0.3 meters) above the water. Almost all chars disappear within ten years, sending landless families scrambling to find new homes.

As they nourish farmlands, monsoons can also cause damage and deaths. In 1995 alone, more than a thousand people died because of monsoons in Bangladesh, Pakistan, and Nepal.