A spell of thunderstorm on Thursday evening brought relief from the hot and humid conditions.
A tree was uprooted on Bentinck Street near Lalbazar, disrupting traffic.
The Met office has not ruled out another thunderstorm on Friday.
The day was bright and sunny, and the humidity took a toll on people. Clouds started appearing late in the evening.
Around 4.15pm, the Met office issued a thunderstorm alert for Calcutta and South 24-Parganas over the "next two to three hours". By 5.30pm, the sky had turned pitch black.
The early evening was breezy and the winds picked up speed after 5pm. The Met office recorded a maximum wind speed of around 45km an hour in Alipore around 5.40pm.
What started as a drizzle soon picked up intensity. By 6pm, the rain had reduced visibility at several places. Now and then, a streak of lightning lit up the night sky.
The maximum temperature on Thursday was 34.3 degrees. The relative humidity was on the higher side. The showers cooled the parched surroundings.
The Met office linked the showers to two weather systems.
An east-west trough now runs from east Madhya Pradesh to south Assam across North Chhattisgarh, Jharkhand, Gangetic West Bengal, Bangladesh at 0.9km above mean sea level. A cyclonic circulation lies over Bihar and neighbourhood at 1.5km above mean sea level. Due to favourable wind patterns and strong moisture incursion from Bay of Bengal, thunderstorms with lightning and strong gusty surface wind are very likely to occur," said a Met bulletin.
The winds felled a tree on Bentinck Street near Lalbazar. Traffic had to be diverted via GC Avenue till the debris was cleared.
Districts like Bankura, Birbhum, West Midnapore, Jhargram, Hooghly, Nadia, Howrah and North 24-Parganas also received thunderstorms on Thursday. North Bengal was also drenched.