Today (30.12.2021)
Thunderstorm with moderate rain is likely to occur at a few places over Coastal Tamilnadu.
Thunderstorm with moderate rain is likely to occur at many places over Villupuram, Cuddalore and Delta districts, Puducherry & Karaikal.
Light rain is also likely to occur at isolated places over Interior Tamilnadu districts.

Tomorrow (31.12.2021)
Thunderstorm with heavy rain is likely to occur at isolated places over Cuddalore, Villupuram and Mayiladuthurai districts, Puducherry & Karaikal.
Thunderstorm with moderate rain is likely to occur at many places over rest Coastal Tamilnadu districts.
Thunderstorm Light to moderate rain is also likely to occur at a few places over Interior Tamilnadu districts.

HEAVY RAINFALL WARNING:

Tomorrow (31.12.2021):
Heavy rain is likely to occur at isolated places over Cuddalore, Villupuram and Mayiladuthurai districts, Puducherry & Karaikal.

THUNDERSTORM WARNING:
Today(30.12.2021) & Tomorrow(31.12.2021):
Thunderstorm with lightening is likely to occur at isolated places over Tamilnadu.

LOCAL FORECAST FOR CHENNAI CITY AND NEIGHBOURHOOD:
For next 24 HRS: Sky condition is likely to be generally cloudy. Thunderstorm with moderate rain, heavy at times is likely to occur in some areas.
Maximum and minimum temperature is likely to be round 30˚C and 24˚C respectively.

Reference:
http://imdchennai.gov.in/tn_fc.pdf
http://www.imdchennai.gov.in/hrw_district.htm