During the monsoon months, July to September the relative humidity is generally high in the state of Rajasthan. The humidity is about 45%-47% in June, which rises to a little less than 70% during August in West Rajasthan and to about 76%-77% in East Rajasthan. The Graph depicts the humidity regime in the state from 1980 to 2009. The average annual humidity percentage during these 30 years was 55.4 %. The trend line in the figure shows a gradual decrease in humidity percentage in the state from 1980 to 2009.
The diurnal variation in relative humidity is least during monsoon in the East Rajasthan; on the contrary it is higher in West Rajasthan. In the summer afternoons the relative humidity is least, i.e. about 20 to 30% in most of the state which makes the summer very dry and hot. In the winters (January and February) the diurnal variation is highest.
Air temperature and relative humidity conditions
The pleasant winters in the state witness mean night temperatures above 4.7oC to 10.6oC. During summers the western Rajasthan becomes the hottest place in the country with mean maximum air temperatures varying from 38.6oC to 42.6oC in May. The recorded extreme temperatures in the state were -4.4oC to 50.0oC in the western Rajasthan and -2.8oC to 47.8oC in the eastern Rajasthan (Indian Meteorological Department, 2010).
The relative humidity in the arid region of Western Rajasthan is also quite high because of the unfavorable circulations of the atmosphere and low precipitation that occurs in the arid region as compared to other semi-arid and sub-humid regions.