Regional Climate Zones of Rajasthan

Beyond the Köpppen system, Indian geography textbooks and RPSC syllabus use a four-zone regional classification based on rainfall distribution — the practical framework used by agriculturalists, planners, and state government.

Zone I: Western Arid Desert Zone

Rainfall: < 10 cm annually (Jaisalmer) to ~25 cm (western Barmer)
Districts: Jaisalmer, western Barmer, parts of Bikaner
Temperature: Summer max 45–51°C; winter min 0–5°C; extreme diurnal range
Key characteristics:

• Sand dunes cover 58% of this zone
• Vegetation: sparse xerophytes — khejri (Prosopis cineraria), cactus, sparse grass
• Humidity: 25–30% (extremely low)
• Evapotranspiration greatly exceeds precipitation — hyper-arid desert conditions
• Phalodi (Jodhpur district edge): recorded India's highest temperature of 51°C on May 19, 2016 (IMD, confirmed record)

Zone II: Semi-arid Zone

Rainfall: 10–50 cm annually
Districts: Jodhpur, Nagaur, Bikaner, Churu, Sikar, Jhunjhunu, Ganganagar, Hanumangarh, Jalore, Pali
Temperature: Summer max 40–46°C; winter min 2–8°C; cold waves in December–January
Key characteristics:

• Transitional zone — crop agriculture possible but highly drought-dependent
• Major crops: bajra (pearl millet), guar, moth, sesame — all drought-tolerant
• Churu records unusual extremes: has registered both 50°C+ in summer and sub-zero in winter in the same year — the widest annual range (50°C+) in India
• Winter rainfall from Western Disturbances (3–6 cm) supports rabi crops (wheat, mustard) in this zone

Zone III: Sub-humid Zone

Rainfall: 50–100 cm annually
Districts: Jaipur, Ajmer, Alwar, Bharatpur, Dausa, Tonk, Sawai Madhopur, Bundi, Chittorgarh (northern), Sirohi, Rajsamand, Udaipur (northern)
Temperature: Summer max 38–44°C; winter min 5–12°C; pleasant winters
Key characteristics:

• Most densely populated agricultural zone of Rajasthan
• Crops: wheat, mustard, maize, groundnut, bajra, jowar (see Topic #87)
• Monsoon dependence: failure of the SW monsoon by even 30% triggers drought conditions
• Aravalli piedmont sub-zone (Ajmer-Udaipur corridor) has slightly higher rainfall from orographic effect

Zone IV: Humid Zone

Rainfall: >100 cm annually (with some areas receiving 80–100 cm being borderline)
Districts: Kota, Baran, Jhalawar, Banswara, Dungarpur, Chittorgarh (southern), Udaipur (southern)
Temperature: Summer max 36–40°C; winter min 8–14°C; moderate extremes
Key characteristics:

• Hadoti plateau (Kota-Baran-Jhalawar) receives 80–100 cm; Vagad (Banswara-Dungarpur) receives 90–110 cm
• Rice cultivation possible (Baran's rice bowl designation)
• Mt. Abu: ~150 cm — exceptional microclimate at 1,722 m; classified separately as sub-temperate humid
• Minimum drought risk; floods occasionally from Chambal and Mahi rivers

Rainfall Gradient — West to East

The most important climatic fact about Rajasthan is the sharp west-to-east rainfall gradient:

Location	District	Average Annual Rainfall
Jaisalmer	Jaisalmer	~10 cm (India's driest district HQ)
Barmer	Barmer	~20–25 cm
Jodhpur	Jodhpur	~35 cm
Ajmer	Ajmer	~52 cm
Jaipur	Jaipur	~55 cm
Kota	Kota	~70 cm
Jhalawar	Jhalawar	~85–90 cm
Mt. Abu	Sirohi	~150 cm (state maximum)

Source: India Meteorological Department (IMD), Jaipur; Rajasthan Agriculture Statistics 2024-25

This gradient — a 15-fold difference between Jaisalmer and Mt. Abu — is the defining ecological and agricultural characteristic of Rajasthan. It underlies crop patterns, population distribution, and irrigation dependence (see Topic #87 and Topic #85).

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