12 Kolkata: An intense downpour late on Tuesday night dragged the mercury down significantly, with both the maximum and minimum temperatures plunging below the normal mark. The Met office has not ruled out more spells until Thursday before the mercury begins to rise again.A combined impact of an upper air circulation, intense heating and moisture in abundance resulted in the sharp thundershower spells in the city late on Tuesday night. The 38 mm of rain, mostly within two hours, cooled the city by dragging down the mercury by around 5°C instantly. The shower was also accompanied by gusty wind and lightning.On Wednesday, the minimum temperature nosedived to 23.2°C. At 4.6 notches below the normal mark, it was a straight drop of around six notches from Tuesday. The maximum temperature, at 32.2°C, which was 3.6 notches below the normal mark, also slipped by 5.5°C from Tuesday."In addition to local thunder cell formations, more thunder clouds reached the city sky, mostly from the northwest direction, by late on Tuesday night, triggering the downpour. We can expect a few more thunderstorm spells until Thursday," said meteorologist HR Biswas, head of the weather forecast section at the Regional Meteorological Centre, Kolkata.The city sizzled without any rain for five days before Tuesday night's nor'wester. Even as more such spells are expected, the Met officials said the intensity is likely to be less. The 60% probability of rain on Wednesday night will go down to 40% on Thursday. Even if the rain is likely to be less intense, a partly cloudy sky will continue to protect the city from the scorching sun."Tuesday's upper air cyclonic circulation over east Bihar now lies over north Bangladesh and its neighbourhood at 0.9 km above mean sea level. Under the influence of the above meteorological condition, thunderstorms with lightning, gusty winds, and heavy rain are likely to occur over some districts of Bengal during Wednesday and Thursday," said an IMD special weather bulletin on Wednesday.But the city is likely to enter another dry spell from Friday onwards, facilitating the mercury to rise once again. "We can expect the mercury to rise by three to four degrees once the thundershower activities come to a halt," said Biswas.Even as the city got only traces of rain till late Wednesday night, districts like Howrah, Hooghly, North and South 24 Parganas, Bankura, Birbhum, West and East Burdwan, and Murshidabad received thundershowers.