Delhi sizzled on Thursday, marking the season's second hottest day yet. The India Meteorological Department (IMD) has issued a yellow alert, which means be aware, for heatwave conditions on Friday and Saturday. The mercury is predicted to rise to 41-43 degrees Celsius. The maximum temperature at Safdarjung, the city's base station, was 41.2 degrees Celsius on Thursday, four notches above normal and 1.6 degrees higher than Wednesday's maximum. Delhi recorded its highest maximum of the season on April 21 at 41.3 degrees. However, the Ridge Observatory in north Delhi on Thursday was the hottest at 42.7 degrees Celsius. The minimum stood at 20 degrees Celsius, three degrees below normal. A Met official said that due to the clear skies and dry westerly winds, the mercury is expected to show a rising trend. Temperatures are likely to be in the range of 41-43 degrees Celsius during April 25-26. It will be above normal by 3-4 degrees Celsius over different parts of Delhi, with the likelihood of heatwave conditions on April 25-26," the official said. A heatwave day is declared when the maximum is 4.5 degrees or more above he normal temperature, and the maximum is at least 40 degrees Celsius. A heatwave is also considered if the maximum temperature reaches 45 degrees Celsius. The IMD has advised people to take precautions for the heatwave. "It may cause moderate health concerns for vulnerable people, including infants and elderly people with chronic diseases," it said. IMD has asked people to avoid heat exposure, wear lightweight, light-coloured, loose, cotton clothing, and cover their heads with a cloth, hat, or an umbrella. Delhiites reeled under the heatwave for three consecutive days at Safdarjung from April 7 to 9, when the mercury stayed above 40 degrees Celsius. Other parts of the city were under a heatwave on April 10. The city also recorded warm night conditions for two straight days. However, rain along with gusty winds on the evenings of April 10 and 11 provided relief. Delhi's air quality remained poor for the fourth consecutive day. The AQI was 227 on Thursday. It is likely to remain poor on Friday, according to the Air Quality Early Warning System for Delhi.