With Southwest Monsoon getting into the last phase Bay of Bengal is set for another Low Pressure area that is likely to develop in the next 24 hours or so off the coast of Andhra Pradesh / Odisha. Thanks to the developing system parts of North Tamil Nadu including Chennai got some spells of rains last night as thunderstorms moved in from the Rayalseema region. 
Southern suburbs and places slightly to the south of Chennai recorded the heavier spells of rains compared to the central parts of the city. Things are expected to be similar today as well with cloudy conditions continuing through the day for Chennai with spells of rains at times as the circulation moves around the rain bands over Peninsular India. 
As the Low Pressure in Bay of Bengal takes shape South India is likely to see increased rainfall activity particularly in the states of Andhra Pradesh , Telengana & Maharashtra. The circulation is tilted to the South as it gains altitude which could provide for heavier rains to concentrate to the Southwestern side of the circulation. Today we are likely to see parts of Coastal Andhra around the Central Coast and adjoining parts of Telengana enjoy spells of heavy rains as the upper air cyclonic circulation develops into a Low Pressure area.
North Tamil Nadu could see cloudy skies with isolated spells of rains at times. There is a fair possibility of some moderate to heavy spells of rains happening later in the night / early morning with supportive wind conditions.