Monsoon

Monsoons are seasonal reversals of wind direction that cause dramatic changes in precipitation patterns. The Asian summer monsoon — driven by the differential heating of land and ocean — is the largest weather system on Earth, delivering 80% of India's annual rainfall in 4 months (June–September). Three billion people depend on monsoon rains for food and water. Monsoon failure triggers famine — Indian droughts of 1876–78 and 1943 each killed millions. Conversely, excessive monsoons cause catastrophic flooding. Climate change is intensifying both extremes: more intense rainfall events, longer dry periods, and unpredictable onset timing. The Indian monsoon's interplay with ENSO (El Niño Southern Oscillation) makes it partly predictable but never certain.