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why there is no rain in rajasthan ?
The climate of Rajasthan state varies from arid to sub-humid.  To the west of the Aravalli range, the climate is characterised by low rainfall with erratic distribution, extremes of diurnal and annual temperatures, low humidity and high wind velocity.  The climate is semi-arid to sub-humid in the east of the Aravalli range, characterised by more or less the same extremes in temperatures but relatively lower wind velocity and high humidity with better rainfall.  The entire state is characterised by hyperthermic conditions.

The annual rainfall in the state varies significantly.  The general trend of Isohytes is from north-west to south-east.  There is a very rapid and marked decrease in rainfall west of the Aravalli range making western Rajasthan the most arid part.  The average annual rainfall in this part ranges from less than 10 cm in north-west part of Jaisalmer (lowest in the state), to 20 to 30 cm in Ganganagar, Bikaner and Barmer regions, 30 to 40 cm in Nagaur, Jodhpur, Churu and Jalor regions and more than 40 cm in Sikar, Jhunjhunun and Pali regions and along the western fringes of the Aravalli range.  On the eastern side of the Aravalli range, the rainfall ranges from 55 cm in Ajmer to 102 cm in Jhalawar.  In plains, Banswara (92.0 cm) and Jhalawar (95 cm) districts receive the maximum annual rain.  Mount Abu (Sirohi district) in the south-west, however, receives the highest rainfall in the state (163.8 cm).  The yearly total rainfall is highly variable at different places all over the state and it is most erratic in the western half with frequent spells of drought, punctuated occasionally by heavy downpour in some years, associated with the passing low pressure systems over the region.

The southwest monsoon which has its beginning in the last week of June in the eastern parts, may last till mid-September.  Pre-monsoon showers begin towards the middle of June and post-monsoon rains occasionally occur in October.  In the winter season also, there is sometimes, a little rainfall associated with the passing western distribution over the region.  At most places, the highest normal monthly rainfall is during July and August.  The number of rainy days during this period varies widely in different places, ranging from 10 in Jaisalmer to 40 in Jhalawar and 48 in MountAbu. Rainfall during the rest of the period ranges from 2.1 cm at Jaisalmer to 7.2 cm at Jaipur, distributed over 2.5 to 6 rainy days.


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