Bone-chilling cold continued to sting east and north India on Tuesday with the mercury nosediving to seven-year lowest in Kolkata.West Bengal capital Kolkata recorded a low of 9.9 degree Celsius — the lowest in seven years, while hill station Darjeeling at -1.0 deg C was the coldest in the state.Kolkata had recorded minimum 9.4 deg C on January 6, 2004. A cold wave alert has been sounded in 10 districts in the state. Severe cold conditions continue to prevail in Uttar Pradesh.Agra at minimum 1 deg C was the coldest place in the state. Lucknow recorded a minimum of 1.4 deg C, six notches below normal.Chill intensified in Bihar as north-westerly winds continued to sweep the region, prompting the state government to announce closure of all schools till January 14.Gaya at minimum 3.9 deg C was the coldest in the state. The minimum temperature in state capital Patna settled at 5.5 deg C as against 8.5 deg C recorded on Monday.Low temperature coupled with icy winds made life miserable for the people in Delhi where the minimum temperature settled below the normal level.The minimum temperature was recorded at 4.6 deg C, two degrees below normal for this time of the year. However, there was no dense fog in the city and flight operations were normal at the IGI airport.