Gurugram on Thursday witnessed its hottest day in April in over 40 years at 45.6 degrees Celsius, according to the India Meteorological Department data. Gurugram had recorded the highest maximum temperature of 44.8 degrees Celsius in the month of April in 1979. Notably, IMD has issued a heatwave alert for south Haryana districts, including Gurugram, for the next four days.