As we slowly get to second week of February though nights & early mornings remain fairly cool & pleasant across most parts of Tamil Nadu, the interior areas of the state during the day gradually undergo a transformation during the day time. Clearer skies during the day time due to drier conditions set the stage for temperatures to increase which then benefits from favorable surface winds that increase the temperature feel during the afternoons.
Parts of South Tamil Nadu & West Interior TN are the early pace setters in this annual heat relay though it becomes essential to mention across the Indian Sub Continent the early pace setters for heat is places in the West Coast which feel the influence of the Easterlies carrying heat across the land mass during the months of January & February. As the effect of winter wanes over Central India and adjoining region places in these areas slowly start getting heated up during the afternoons with NW India joining the party much later.
It is interesting to note east coast of Tamil Nadu & parts of Coastal AP falling under the rain shadow region of Southwest Monsoon sees increased heat when strong Westerlies / Northwesterlies push the heat from landmass onto the coast. This situation is more intense when Monsoon is still not fully established & atmospheric moisture availability remains limited.
Ironically as the rest of the state gets heated up during the day time, Chennai and other coastal places get benefitted from the Easterlies which modulates the day time maximum temperatures keeping it under check. Most years we have the Easterlies to thank until late April and in some instances even up to mid of May we enjoy the support from Easterlies that have enough moisture to keep the heat away.