A 60 kmph nor'wester swept across Kolkata and adjoining districts on Wednesday evening, bringing relief from the hot and humid conditions prevailing over the past few days. The India Meteorological Department (IMD) had forecast severe thunderstorm activity accompanied by lightning, heavy rain and gusty winds over parts of Kolkata, Howrah, North and South 24 Parganas, Purba Medinipur and Hooghly districts. A squall passed over the city from the northwesterly direction, reaching a maximum wind speed of 60 km per hour, the IMD said. Dark clouds engulfed the sky over Kolkata and adjoining areas as strong winds and rain, along with thunder, forced people indoors. Temperatures dropped sharply, providing respite from the heat. The Met office said the southwest monsoon, which has already advanced into sub-Himalayan West Bengal, is expected to cover the remaining parts of the state in the next three to four days. The IMD has forecast very heavy rain in the north Bengal districts of Jalpaiguri and Alipurduar and in Darjeeling, Kalimpong and Cooch Behar districts till Friday morning and heavy rain thereafter in all these districts till June 14. Kolkata recorded 24 mm rainfall, while Dum Dum airport received 32 mm rain from 8.30 am to 5.30 pm on Wednesday, the IMD said. Barrackpore in North 24 Parganas district recorded the highest rainfall in south Bengal during the period at 54 mm, it said.