The north east monsoon will hit coastal areas of Tamil Nadu and Puducherry during the next 24 hours before gradually extending to other parts of the region, regional weather office here said Wednesday.
With a month's delay in arrival of the three-month-long (October to December) monsoon, the met department said the next two months would be crucial.
Last month, the Indian Meteorological Department (IMD) had forecast 12 per cent surplus rainfall for Tamil Nadu from the north east monsoon (NEM).
Director of Area Cyclone Warning Centre, S Balachandran said coastal areas of Tamil Nadu and Puducherry would first experience north east monsoon in the next 24 hours.
"It would gradually extend to rest of Tamil Nadu and adjoining areas of south Karnataka and Kerala during the subsequent days," he said.
Attributing the delay in the onset of monsoon to Cyclone Titli and Luban that formed over Bay of Bengal and Arabian Sea, respectively, early this month, Balachandran said the next two months would be crucial.
"We will have to wait and watch," he said.
Chennai and adjoining areas such as Ennore, Kelambakkam and Mahabalipuram recorded five cm rainfall each in the last 24 hours, as against one cm recorded the day before.
Tamil Nadu depends on north east monsoon, also known as retreating monsoon, as it brings much of the annual rainfall to the state.