New Delhi, April 17 -- The Capital on Thursday recorded its hottest day for the season, again, as temperatures soared, crossing the 40degC-mark at the city's base station for weather. Simultaneously, the air quality also deteriorated into the 'poor' category, prompting the reimposition of Graded Response Action Plan (Grap) restrictions, a month after they were fully lifted. According to official forecast, the mercury is expected to rise further and may even soar to 42degC on Friday. On Monday, the base station of Safdarjung recorded a maximum of 40.3degC, which is 3.5 degrees above normal for the year. However, the highest maximum across the city was 41.4degC at the Ridge station in north Delhi. This follows the trend with temperatures rising steadily over the last few days- primarily due to clear skies and lack of western disturbances in the region since April 7 and 8. Delhi's maximum on Wednesday was 39.1degC; 38.2degC on Tuesday; 36.1degC on Monday; and 34.7degC on Sunday. Delhi's air quality also stayed in the 'poor' category on Thursday. Noting this, the Commission for Air Quality Management (CAQM) in NCR to invoked Grap stage-1 (poor) measures with immediate effect across NCR. This mainly includes preventive, rather than restrictive measures, including increased sprinkling of water, use of mechanised sweepers on roads, enhanced frequency of public transport, and strict vigilance of dumping of waste as well as industrial emissions, among others. All Grap restrictions had been lifted on March 16 after air quality improved to the 'moderate' category....