Climate and Monsoon of Rajasthan

Koppen classification and climatic regions

Under the Koppen climate classification, the Thar Desert region of western Rajasthan (around Jaisalmer, Bikaner, Phalodi, Churu, Sri Ganganagar, Hanumangarh) falls under the 'BWhw' category, denoting a hot arid desert climate — marked by very low rainfall and extreme temperature swings, a large gap between day and night and between summer and winter. The Aravalli range roughly splits Rajasthan into two climatic halves — arid and semi-arid country to the west of the Aravallis, and a comparatively wetter sub-humid zone to the east.

Mount Abu (Sirohi district), home to Guru Shikhar, the Aravallis' highest peak, is considered the state's wettest spot — its climate is markedly cooler and more humid than the rest of the state. Jaisalmer district, by contrast (especially the area around Sam), receives the least rainfall in the state and is considered close to the 10 cm annual rainfall isohyet.

The two monsoon branches

Rajasthan gets roughly 90% of its annual rainfall during the June-September south-west monsoon, which arrives via two branches. The Arabian Sea branch runs roughly parallel to the Aravalli range (since the Aravallis run south-west to north-east), so it cannot take full advantage of the orographic barrier and delivers relatively little rain to western Rajasthan — something like a rain-shadow effect. The Bay of Bengal branch, by contrast, brings more rain to eastern Rajasthan (particularly the south-eastern Hadoti region — Kota, Bundi, Jhalawar, Baran), since it arrives after crossing central India.

This is why Rajasthan's typical rainfall order runs: south-eastern Rajasthan (the wettest plains) > eastern Rajasthan > western Rajasthan (the driest, the Thar Desert). Mount Abu, sitting in the Aravalli hills, is the exception to this general pattern because altitude brings it extra rainfall.

Local climate terms

Mawath (Mawat)

Winter rain between December and March caused by western disturbances (Mediterranean-origin weather systems), considered highly beneficial for rabi crops (wheat, mustard, gram) — farmers call it the 'life-giver of the rabi season'.

Loo

Extremely hot, dry winds that blow across western and north-western Rajasthan during the summer months (April-June), a major cause of heat-stroke.

Rain-shadow effect

The situation where western Rajasthan does not receive adequate rainfall because the Arabian Sea monsoon branch runs roughly parallel to the Aravalli range.

Temperature and seasons

Rajasthan is generally considered to have three main seasons — summer (March-June), the monsoon/rainy season (July-September), and winter (October-February). In the western desert districts, summer temperatures can climb well above 45°C, while winter nights can fall quite low — meaning both daily and seasonal temperature swings are large. Churu and Sri Ganganagar are often cited as examples of extreme temperatures, both scorching heat and severe cold. Sandy soil heats up fast during the day and cools down fast at night, which is why desert regions see especially large diurnal temperature variation.

For REET Mains, the reference pair worth locking in is Churu and Sri Ganganagar for extreme heat and extreme cold alike, with Mount Abu anchoring the cooler, wetter end of that same spectrum — keeping these two ends of the range in mind makes a temperature-based question much easier to answer quickly.

Desertification and the effect of the Indira Gandhi Canal

A large part of western Rajasthan has struggled with desertification — the process by which fertile land turns sandy and unproductive over time, worsened by overgrazing, deforestation and erratic rainfall. To tackle this and bring irrigation to the Thar region, the Indira Gandhi Canal (earlier known as the Rajasthan Canal) was built — it draws water from the Harike Barrage in Punjab and reaches districts like Sri Ganganagar, Bikaner and Jaisalmer. This canal has significantly reshaped western Rajasthan's agricultural landscape — an area once limited to livestock rearing and rain-fed farming can now support irrigated agriculture, though this has also brought new challenges around local water management and soil salinity.

From a climate-geography perspective, Rajasthan can broadly be divided into four sub-regions — the western arid desert region (Thar), the north-eastern semi-arid plains region, the south-eastern comparatively humid Hadoti plateau region, and the southern Aravalli hill region, which includes the exceptionally humid Mount Abu. It is useful for REET Mains to have this four-way classification in brief, since it connects climate, soil and vegetation together.

Why this matters for REET Mains

The climate topic rests on geography-based facts, so map-sense helps a lot here — understanding 'which direction, what' works better than rote memorisation. The most common mistake is swapping the Arabian Sea and Bay of Bengal branches — remember, the Bay of Bengal branch is more effective for Rajasthan (bringing more rain to the eastern/south-eastern part), while the Arabian Sea branch stays relatively ineffective because it runs parallel to the Aravallis. This runs counter to the common assumption that being closer to the Arabian Sea should mean more rain, and that very contradiction is exactly what exam questions are built around. A simple habit that helps here: whenever a question names a place, first locate it mentally relative to the Aravalli range, and the correct monsoon branch and likely rainfall pattern usually become obvious from there.

Practice questions

Frequently asked questions

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