New Delhi, Nov. 17 -- An orange alert indicating heavy rainfall has been issued for parts of Tamil Nadu and the capital, Chennai, due to the presence of an upper-air circulation - a low-pressure system that has formed over the Bay of Bengal. According to the weather agency, heavy to very heavy rainfall is expected in the southern state over the next four days.

Chengalpattu, Chennai, Kancheepuram, Villupuram, Cuddalore, Ariyalur, Mayiladuthurai, Nagapattinam, Thanjavur, Tiruvarur, Pudukkottai and Ramanathapuram districts of Tamil Nadu, along with Puducherry and the Karaikal region, have been placed under an orange alert.

Light to moderate rainfall has been forecast for Tiruvallur, Kallakurichi and Perambalur districts.

In view of the he...