12 Kolkata: The mercury started spiralling up on a warm and humid Monday, even as the maximum temperature touched 35°C. While it is likely to hover around the 35°C mark for the rest of the week, chances of thunderstorms across south Bengal have also brightened, said the Met office.A bulletin issued by the Regional Meteorological Centre stated: "An east-west trough runs from Punjab to north Bangladesh across Haryana, south Uttar Pradesh, south and north Gangetic Bengal at 1.5 km above mean sea level. Also, in the presence of a favourable wind pattern and moisture incursion from the Bay of Bengal, enhanced thunderstorms with gusty winds..." It went on to add that thunderstorms and heavy rain at one or two places were likely across the districts of south Bengal till May 22.A thunderstorm and a spell of rain on Saturday pulled the mercury down by five degrees on Sunday. With moisture flowing in from the sea with southerly winds, more thunderstorms and rain are likely over the next two days, said the Met office.