Seasons of India

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Temperature: Cool to cold; January is coldest month; Northern Plains 10–15°C; Delhi can drop to 3–5°C; Himalayan valleys below 0°C
Rainfall: Western Disturbances bring 5–7 cm of rain/snowfall to NW India (Punjab, Haryana, HP, J&K); rest of India is dry
Wind: Cold northwesterlies (from Central Asia); Himalayan barrier reduces their intensity
Fog: Dense winter fog affects Delhi, Haryana, Punjab — disrupts transport (IGI Airport flight delays common)
Agriculture: Rabi crops (wheat, mustard, chickpea, barley) grow during this season

Temperature: Rises rapidly; May is hottest month; Rajasthan, MP, UP reach 45–50°C
Loo winds: Hot, dry, dusty winds from west-northwest blow over Punjab to Bihar; cause heat stress, heat strokes
Pre-monsoon thunderstorms: Local convective storms in different regions:
- Nor'westers (Kalbaisakhi): Thunderstorms in West Bengal, Assam (important for jute and tea)
- Mango Showers: Pre-monsoon rains in Kerala and Karnataka — beneficial for mango and coffee
- Blossom Showers: Rains in Kerala — help coffee flowering
- Andhi: Dust storms in Rajasthan/UP before monsoon
Agriculture: Kharif crop sowing begins with first monsoon rains

India's most important climatic season; accounts for 70–90% of annual rainfall
Onset: Kerala June 1; full coverage by July 15; withdrawal starts NW India in September
Monsoon "breaks" (active/break spells): Monsoon has active periods (heavy rain) alternating with break periods (dry intervals — ITCZ shifts north toward Himalayas)
Active monsoon: Heavy rainfall over Peninsular India and Bengal; major rivers swell
Break monsoon: Dry in Peninsula; heavy rains along Himalayas and NE
Flood zones: Assam (Brahmaputra floods), Bihar (Kosi floods), Mumbai (Mithi River), Uttarakhand (2013 flash flood — ~5,000+ deaths)

SW Monsoon withdraws from NW India by September; retreats from entire North India by October 15; withdraws from South India by December 1
As the system retreats, dry northwest winds establish over the country
Northeast (NE) Monsoon: Bay of Bengal wind system; winter northeasterlies pick up moisture over Bay of Bengal and deliver it to Tamil Nadu, southern AP, and Sri Lanka
Tamil Nadu's annual rainfall: ~900 mm (60% from NE monsoon, October–December)
Cyclones: Bay of Bengal becomes more active during Oct–Nov; 80% of India's tropical cyclones form during this period (e.g., Cyclone Gaja, Amphan, Nivar)
October heat: After monsoon retreats, humidity + heat creates oppressive October heat in NE India