It has been raining heavily in Tamil Nadu since the onset of the north east monsoon on October 12, but no respite is in sight, with yet another low pressure trough forming in the southwest Bay.

The weather office in Chennai said a new, feeble trough of low pressure lay over southwest Bay off the Tamil Nadu coast and under its influence, many places in the state and Pondicherry were likely to receive rain or thundershowers during the next 48 hours.

There would be isolated heavy downpour in the state and the Union Territory in the same period, the weather office said adding, the city and suburbs would be cloudy with one or two spells of rain.

The low pressure trough posed a fresh threat to the state, already ravaged by heavy downpour and floods caused by four distinct systems, including 'Baaz' which brought heavy rain and 'Fanoos' the cyclonic storm which crossed the coast on December 10.

Incessant rains lashed out the southern districts under the impact of 'Fanoos' and forecast of further rains is a serious threat.

The city and its suburbs were also battered by heavy rains and anything further would make life more miserable.

Velachery, Madipakkam, Vijayanagaram, Ram Nagar, Selaiyur, Keezhakattali in south Chennai and Korattur, Ambattur, Villivakkam, Kolathur, Ennore and Manali areas in the north were still submerged under sheets of water, with hundreds of people marooned.

Sources in the weather office, however, refused to attach much significance to the trough of low pressure, saying it was usual during the monsoon and that the rains were only "seasonal rains".