Wet spell and easterlies likely to bring relief from peak summer heat in State for a week

Mild showers continued in several parts of Chennai on Friday. Agni Natchathiram or the peak summer period is set to take a backseat till May 14 as heavy rainfall is likely to persist in the south and interior parts of the State.

Twenty-two south and interior districts, including Tenkasi, Thanjavur, Madurai, and the Nilgiris, are likely to receive isolated heavy rainfall with gusty winds till Sunday.

The Regional Meteorological Centre (RMC) has forecast that the maximum temperature will gradually dip by two-three degrees Celsius and remain below normal in Tamil Nadu till May 12.

Easterly winds will keep temperature levels in check in coastal places for a week.

On Friday, Salem recorded 36.6 degrees Celsius, the highest maximum temperature in the State. Chennai recorded a below-average temperature of 33 degrees Celsius. An upper air cyclonic circulation that lies over Comorin area and another trough running from Comorin area to southwest Madhya Pradesh influenced the wet weather over Tamil Nadu.

According to the RMC, many places over south T.N. and a few places over northern districts are likely to receive light to moderate rainfall over the weekend. The prevailing weather systems would also bring light to moderate rainfall in some areas of Chennai on Saturday and reduce day temperature.

Meteorologists noted that Chennai is yet to enter its peak summer phase as strong westerlies have not set in this month. Usually, the second half of May is considered hotter, with the average temperature climbing to 37-38 degrees Celsius.

On Friday, Chennai recorded 31 degrees Celsius at 4.30 p.m. and a humidity level of 75% owing to easterly winds.

Offset humidity

Y.E.A. Raj, former Deputy Director General of Meteorology, RMC, said cool easterlies play a decisive role in comfortable weather in coastal places like Chennai and it would offset the increase in humidity by bringing down the temperature levels.

Citing his research paper on variations of temperature and humidity in Chennai owing to sea breeze, he said the maximum temperature dips by 2.4 degrees Celsius in May within an hour of sea breeze onset.

He said that at the same temperature – for instance 36 degrees Celsius, a place like Coimbatore with a lower humidity of 30% would feel less uncomfortable than an area with a humidity level of 70% since drier air allows sweat to evaporate efficiently and cool the body.

In coastal stations, including Chennai, the dip in temperature would offset the increase in humidity owing to sea breeze, leading to cooling effect.