Climate & Soils
Bihar GK · जलवायु और मिट्टी
📋Quick Overview
Bihar has a humid subtropical climate (Köppen classification: Cwa type) with four distinct seasons. The state receives significant rainfall from the south-west monsoon (June–September). North Bihar generally receives more rainfall (up to 1500mm) compared to South Bihar (800–1000mm). The climate extremes are notable — Gaya being the hottest city and North Bihar terai belt being humid and fertile.
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Gaya is the hottest city in Bihar — summer temperatures can reach 47–48°C. It is located in an inland basin surrounded by rocky hills, creating a heat-trap effect. In contrast, northern terai areas near Nepal receive heavy rainfall.
📖Four Seasons of Bihar
| Season | Months | Characteristics |
|---|---|---|
| Winter (Shishir/Hemant) | November – February | Cool and dry; temp 5–20°C; foggy mornings; cold waves from N. India |
| Summer (Grishma) | March – May (June) | Hot and dry; temp 35–47°C; Gaya hottest; hot winds (loo) in May–June |
| Monsoon (Varsha) | June – September | 80% of annual rainfall; SW monsoon; North Bihar gets more (1200–1500mm) |
| Post-Monsoon (Sharad) | October – November | Retreating monsoon; mild weather; festive season (Chhath Puja, Diwali) |
📖Soil Types of Bihar
| Soil Type | Location | Characteristics | Crops Suited |
|---|---|---|---|
| Alluvial Soil (Khadar — new alluvium) | River floodplains (Ganga belt, North Bihar) | Light, sandy, highly fertile, renewed annually by floods | Rice, wheat, maize, vegetables |
| Alluvial Soil (Bhangar — old alluvium) | Older flood plains, slightly elevated areas | Heavier, contains kankar (calcium deposits), less fertile | Wheat, pulses, oilseeds |
| Sandy Soil | North Bihar terai (along Nepal border) | Light, porous, poor water retention, flood-prone | |
| Clayey/Loamy Soil | River valleys (Gaya, Bhojpur, Son valley) | Good water retention, fertile, good for kharif crops | Rice, sugarcane, maize |
| Red Laterite Soil | South Bihar (Jharkhand border — Nawada, Gaya, Jamui hills) | Acidic, iron-rich, less fertile, rocky terrain | Maize, pulses, forest products |
📝Terai Belt & Rainfall Variations
- •Terai belt: North Bihar along Nepal border (Champaran to Kishanganj) — dense forests, rich alluvial soil, high humidity, high rainfall (1400–1600mm).
- •Khadar (new alluvium): Fresh soil deposited by floods each year — most fertile; found in Gangetic plains.
- •Bhangar (old alluvium): Older deposits away from rivers — contains kankar nodules (CaCO3), less fertile than Khadar.