Thunderstorm activity is likely to increase gradually over KTC (Kanchipuram Thiruvallur Chennai) districts from 13th onwards. Thunderstorm activity can be observed over North Tamil Nadu including Chennai over this weekend and this will continue into next week owing to weakening of westerlies in the mid levels of atmosphere. These thunderstorms are more likely to be scattered. So not all places in city will receive rain at same time/same day. If your place is missed out, next or other day there may be rain.
As surface westerlies have weakened a lot, early sea breeze onset will prevent the temperature spike over Chennai and over other coastal districts of Tamil Nadu over the weekend and into next week too.