Heatwaves and monsoon change in India

India's summer monsoon, which arrives in June and withdraws by September or October, supplies most of the country's annual rainfall and shapes sowing, groundwater recharge and hydropower. It is driven by the seasonal heating of land relative to the ocean, which draws moist air inland. Because it depends on a delicate temperature and pressure contrast, small changes in warming, aerosols and ocean temperatures can shift its timing, intensity and geography — not necessarily making India uniformly wetter or drier, but making rainfall more variable.

Heatwaves are a second, linked risk. A heatwave in India is defined by the India Meteorological Department using temperature thresholds that vary by region and by departure from normal, rather than a single national number. Prolonged heat affects outdoor workers, children, older people and those without cooling, and it raises demand for water and electricity at the same time as it stresses crops and livestock. Night-time heat matters too, because bodies and crops recover less when nights stay hot.

Adaptation is partly technical and partly administrative. Heat action plans in cities such as Ahmedabad, first developed after a deadly heatwave in 2010, combine early warnings, public awareness, access to drinking water and shade, and adjustments to work hours. For the monsoon, adaptation means better forecasts, water storage, crop insurance, diversified sowing dates and varieties that tolerate both dry spells and heavy rain.

The equity point is sharp. Those who contribute least to emissions — daily-wage workers, small farmers, slum residents without fans or piped water — often face the worst heat and the least protection. A heat or monsoon policy that only issues warnings, without water, shade, rest and income protection, protects the well-off more than the vulnerable. Cooling centres, shaded bus stops and water points in informal settlements are therefore climate infrastructure, not charity, and should be planned in municipal budgets before summer, not improvised during a heatwave.