Winds, topography and microclimates

Fourth factor: winds. A wind carries a whole body of air, with its heat or cold and its moisture, from one place to another.

Punjab, Haryana, Rajasthan and Madhya Pradesh often get winds from the west that have crossed the deserts from Arabia to Afghanistan. They bring hot, dry air and cause heat waves in summer. In winter, cold winds from across the Himalayas cause cold waves in the foothills.

Winds also change humidity and rain. Winds from deserts are dry; winds from the sea bring moisture, which may fall as rain. Remember this: it's the secret of the monsoon.

Fifth factor: topography, the shape of the land: mountains, hills, valleys, slopes, coasts. The Himalayas and Karakoram shield India from the icy winds of Central Asia's cold deserts. The flat Thar has nothing to stop hot, dry winds. A mountain wall is a shield; a flat plain is an open door.

A region's climate comes from all five factors together: latitude, altitude, the sea, winds and topography. To describe it, we look at its patterns of temperature, precipitation (rain, snow, fog, mist) and wind over three decades or more.

A microclimate is a different climate in one small area, unlike the land around it. Enclosed valleys and some forests have their own. So do urban heat islands: in a city, concrete and roads soak up the sun's heat, so a crowded block of buildings stays much hotter than the countryside nearby.