The word monsoon, which most people understand as a wet period in summer over India and Bangladesh, has a much wider meaning.

Monsoon, which comes from the Arabic word for season, refers not only to the southwesterly winds that blow in from the Arabian Sea in summer, but also the dry northeasterlies across the Asian sub-continent in winter. And it is not only India that experiences monsoons, but many other parts of the world including Africa, Australia and the United States of America.

The Indian summer monsoon, with its life-saving or indeed life-threatening rains, blow in on the southwesterly wind, and can be accurately forecast as to when they will start, but knowing the intensity of the rains as it moves north is more difficult.

The reason for the monsoon is the temperature differential between the land and the sea. From May onwards the land heats up much more quickly than the sea and, in effect, develops a gigantic sea breeze. These very moist southwesterly winds and rain reaches the southern most parts of India around the 1 June and moves north to get to Mumbai by about the 10 June.

The annual rainy period has a profound effect on the agriculture of the sub-continent where most of the population are subsistence farmers and are dependant on the rain to grow their crops. In fact the monsoon brings some 90% of India's annual water supply. Too much rain, or too little, means the difference between flood and famine.

These monsoon rains can end during September almost abruptly as they start as the sun begins to lose its power to heat the land sufficiently to keep the sea breeze going.

So what is it like for the people of India waiting to see what the southwesterly monsoon will bring?

Well during May the temperatures start to soar getting up to over 40 degrees Celsius or 100 degrees Fahrenheit, and remember these are temperatures measured in the shade! Over most of the world the afternoons are periods to enjoy but not here. The heat is so searing that virtually everything stops. It is too hot even to move and there is no air conditioning or indeed enough water to cool down. The children sit in darkened classrooms away from the sun and just wait for dusk to arrive, but even then the nights are so uncomfortable it is difficult even to breathe. Everyone is looking to the southwest for the first hint of the rains, the humidity builds up making life even more unbearable, and then the first clouds are seen. Relief is on the way, and with the first rains life starts to take on some meaning again.

In wintertime, with the sea warmer than much of inland Asia, the winds reverse and bring in dry northeasterly winds across much of southern Asia and this is known as the northeast monsoon.

So spare a thought when you sit in the garden with the sun blazing down. You can go inside for a cooling shower, but most of the population of India and Bangladesh have to wait for the natural showers from the huge cumulonimbus clouds.