It is normal that it should be hot and very dry this time of year in India. Every spring, the arid soil of that country is baked lifeless by the burning sun and desiccating winds.
Then, around the end of May, just when the heat seems insupportable, clouds that have been piling up in the distance for some time burst open to disgorge their torrential rains upon a grateful land.
The Indian monsoon system resembles our own sea breeze phenomenon re-enacted on a grand scale. As the heat of the summer sun intensifies, the air over the vast Asian landscape expands and becomes lighter, causing a low-pressure area to develop over the continent. Then, with an anti-clockwise motion around this low, warm moist air from the Indian Ocean is drawn in over India from the south-west, bringing heavy showers, thunderstorms and torrential rain.
The monsoon rains normally continue intermittently until late September, delivering in the few months of their duration about 90 per cent of the subcontinent's annual rainfall. The rains are a vital life-giving force. But now and then they are delayed or are weaker than usual; livestock suffers, agricultural production falls, and great hardships are visited on large sections of the local population.
Sometimes the monsoon fails completely, as has happened for the past two years in Gujarat, Rajasthan and Andhra Pradesh, and the results are tragic.
We cannot blame global warming for the current Indian drought. The summer monsoon rainfall averaged over the whole of India has been stable for 120 years since it was first measured, and shows no signs of systematic change. It is, however, characterised by a very high degree of variability.
It is known, for example, that years when the El Nino phenomenon is in evidence tend to be years when the rains are weak or, in some places, missing altogether. But this is probably not the cause of the present misery on the subcontinent, since the last El Nino was three years ago.
Many other factors play a part, however. The amount of snow on the Himalayas, for example, is known to affect the intensity of the summer monsoon, as does the amount of residual moisture in the soil at certain times. Whatever the reason, extremes might be said to be the norm in many parts of India.
Sometimes, as at present, failure of the monsoons over several seasons causes extreme hardship; at other times the monsoon rains may be exceptionally heavy, and the superabundant waters, flowing over a land baked hard as concrete by the early summer sun, sweep away and drown hundreds of people in their muddy tides.