The western part of Rajasthan is desert. It gets an annual rainfall less than 20 cms. Rajasthan is under the influence of South West Summer monsoons. The Aravallis system lies parallel to the direction of South West monsoons coming from Arabian Sea. So these low mountain system is unable to check these winds, so western Rajasthan is practically dry. The southern parts get some rainfall. This area lies at a great distance from the Bay of Bengal. The Bay of Bengal monsoons become dry and lose their moisture when they reach Rajasthan. Also, Rajasthan and Gujarat are ata great distance from the Himalayan region so, theydo not come under the influence of monsoons giving rain in the sub-Himalayan region. The leeward slopes of Western Ghats remain in rain-shadow, but there is no guarantee of rainfall hence, this area also comes under the drought prone areas of the country.