The Chennai Meteorological Department has said that rain is likely in 12 districts, including Chennai, over the next 2 hours.
An atmospheric circulation is prevailing at an altitude of about 5.8 km over South Coastal Tamil Nadu and adjoining areas.
A weak low-pressure trough is prevailing in the lower atmosphere over the coastal areas of North Tamil Nadu.
As a result, today (Aug. 3), heavy rain accompanied by thunder and lightning and strong winds (at speeds of 40 to 50 km per hour) may occur at one or two places in the hilly areas of Coimbatore district, Nilgiris, Theni, Tiruvannamalai, Villupuram, Cuddalore, Kanchipuram, Chengalpattu districts, and in Puducherry as well.
Moderate rain accompanied by thunder and lightning and strong winds (at speeds of 40 to 50 km per hour) may occur in some places in the other Western Ghats districts, delta districts, Ramanathapuram district, and northern coastal Tamil Nadu, as well as in parts of Karaikal. It has also been stated that light rain accompanied by thunder and lightning may occur in some places in the rest of Tamil Nadu.

In this situation, the Chennai Regional Meteorological Centre has stated in a release that light to moderate rain accompanied by thunder and lightning may occur over the next 2 hours (until 7 PM) in districts including Chennai, Chengalpattu, Tiruvallur, Tiruvannamalai, Kanchipuram, Tirupattur, Vellore, Ranipet, Villupuram, Cuddalore, Ariyalur, Perambalur, and in Puducherry.
