By the end of May, the sun shines 
vertically over the Tropic of CAncer causing a further rise in temperature. A thermal low developing over Rajasthan begins to intensify. The atmospheric pressure in the Gangetic valley Cast trades crossing the equator deflect eastward and approach the southwest "o fall. Most equatorial air is drawn from the Indian ocean. The south Continue COast as the southwest monsoon. The burst of the south west monsoon takes streams). The easterly jet stream replaces the westerly jet stream. due to the sudden changes in the upper tropospheric circulation (jet place

   Temperatures - Temperatures all over the country begin to fall as the monsoon rainfall intensifies. The north-western parts and desert areas of Rajasthan still have temperatures reaching upto 40°C in July. Relative humidity ranges between 80%-90% in the country, with the exception of the desert areas, of course, 

   Rainfall - In early June, the south-west monsoon strikes the Peninsula om the Indian Ocean. The 'burst of monsoon' is associated with sudden cloud burst and lightning. The monsoon engulfs the entire  the onset and retreat of monsoon in the country take place on the following dates :

Due to the Peninsular shape of India, the Southwest Monsoon enters the Indian subcontinent in two currents, blowing from the Arabian Sea and the Bay of Bengal.

 Arabian Sea branch -The south west monsoon hits the coast of Kerala and moves northward into Konkan. The Western Ghats or the Sahyadris, rising to the height of over 1200, confront these monsoon winds. The West Coast and the western slopes of the Sahyadris receive orographic rainfall exceeding 250em. Tle leeward side of the Ghats, being a rainshadow area, receives lesser rainfall (100cm) which decreases eastward (50cm). The leeward slopes receive scanty rainfall which is erratic and often results in droughts. The following table giving the amount of rainfall at various stations during the south west Monsoon is self-explanatory:


    The fact that Mangalore receives 301 cm rainfall, Ratnagiri 253 Mumbai 183 cm and Surat 105 cm reveals that the rainfall decrease northward too. 

       A branch of Arabian Sea monsoon crosses the Western Ghats follows the Narmada valley upto Madhya Pradesh. The northern part of thir branch reaches Himachal Pradesh through Gujarat and Thar desert. Guiara and Rajasthan receive very little rainfall as there are no high mountains c hills to intercept the rain bearirg winds. The low Aravalli hills situated in the direction of monsoon winds do not offer any resistance, hence remain practically rainless

   Bay of Bengal branch - The Bay of Bengal monsoon hits the Arakan and Tenasserim Yoma of Myanmar A branch of it turns westward into the Assam valley and eastward It causes heavy rainfall in Cherrapunji (1080 em) situated in the Khasi hills of Meghalaya. The peculiar funnel-shaped' situation of Meghalaya, surrounded by 1525m high hills, is largely responsible for the occurrence of heavy rainfall in this region. Shillong, situated north of these hills receives only 140 cm rainfall, which further decreases in Guwahati (100 cm). A branch of this monsoon turns westward into the Gangetic valley and reaches upto Punjab. The amount of rainfall decreases westward. Kolkata records a rainfall of 119 cm, Patna 105 cm, Allahabad 76 cm and Delhi 46 cm. The amount of rainfall on the Himalayan slopes to0 decreases westward. Darjeeling records 250 cm rainfall, Mussoorie 206 cm and Shimla 122 cm. Rainfall decreases as one descends from the Himalayan slopes to the Ganga Plain. Nainital records 206 cm, Bareilly 81 cm, while Agra has only 75 cm rainfall. The number of actual rainy days too decreases westrard.
    
       The central part of Northern India receives scanty rainfall as both the branches of monsoon lose their moisture on reaching here. The region of scanty rainfall extends from the Aravallis to Orissa. 

      Frequent tropical cyclones are associated with the south-west monsoon. These cyclones are particularly active in the Bay of Bengal. The delta regions of the Ganga, Mahanadı. Godavari and Kaveri are highly affected by these destructive cyclones from July to November. Cyclonic activity in the Arabian sea remains feeble.