Why Rajasthan and Gujarat Receive less rainfall ??

1) This is because the Aravali Range in Rajasthan lie parallel to the Arabian Sea branch of South West Monsoon, and do not offer any obstruction to the rain bearing winds. By the time, the Bay of Bengal branch of the South West Monsoon reaches to the western part of the country i.e. Gujarat and Rajasthan it do not have sufficient moisture left with to cause rain. Also the same Aravali Range which fails to act as a barrier to the Arabian sea branch, act as a barrier for the Bay of Bengal branch of Monsoon and limit its reach to the eastern side of Aravali i.e. M.P. and Maharashtra.

2) The second reason is that the hot climate of Rajasthan increases the moisture holding capacity of the rain bearing winds, and does not allow it to shed its moisture in Rajasthan.