Rajasthan region receives abundant quantities of solar radiation especially the western parts of the state. The mean duration of bright sunshine in this region is 8.0 to 8.8 hr/day.
- The maximum sunshine period of 9.6 to 9.8 hr/day is in October for western part of Rajasthan whereas it is 10.0 to 10.5 hr/day during April and May for eastern part.
- In rainy month of August the sunshine is available only for about 4.4 to 7.1 hrs/day.
- In a year, Rajasthan has 300-330 days of clear sunshine.
- Even during rainy season of July and August, the skies remain clear for 8-9 days/month in west Rajasthan and for 4-5 days/month in east Rajasthan.
- The cloud cover decreases to a great extent over the entire state during October.
- Fog occurs occasionally due to lack of sufficient moisture in the region.
- The maximum frequency of occurrence of fog is during December and January in both Western and Eastern Rajasthan.
- During the monsoon season hill fog occurs at few places, when air is almost saturated and is easily cooled below the dew point while rising over high elevations.
- The annual potential evapotranspiration values vary widely between eastern and western Rajasthan.
- In Dungarpur and Banswara districts the annual potential evapotranspiration is less than 1300 mm whereas it is more than 2000 mm in Jaisalmer district.