Gurugram / New Delhi, Dec. 19 -- Amid calm winds, low temperatures, and 'poor' air, Gurugram was blanketed under a dense smog on Thursday, causing visibility to drop as low as 100m early in the morning. Similar conditions were reported across Delhi-National Capital Region (NCR), impacting flight and train operations. According to district administration officials, a thick layer of smog enveloped major stretches, including Golf Course Road, around Cyber City, and on the Delhi-Gurugram-Jaipur (NH 48), Dwarka and Kundli-Manesar-Palwal expressways. India Meteorological Department (IMD) said visibility was as low as 100 metres at around 6.00 am in most parts of the city "The dense fog is expected to continue in the region by the end of this week. Temperatures are expected to drop further with almost calm winds, failing to disperse the pollutants," a senior IMD official said. The IMD classifies fog as "shallow" when visibility is between 500 and 1000 metres, as "moderate" when visibility is between 200-500 metres, as "dense" when it is between 50 and 200 metres, and as "very dense" when it falls to below 50 metres. According to the Central Pollution Control Board (CPCB)'s 4pm national bulletin, Gurugram recorded a 24-hour average AQI of 276, placing it in the 'poor' category, with PM2.5 identified as the dominant pollutant. Of the four continuous air quality monitoring stations operational on Thursday, readings at Sector 51 and Gwal Pahari at 7.00 pm time were in the 'very poor' category- 302 and 359, respectively. The station at Vikas Sadan recorded an AQI of 205 ('poor') during the same time period, while the station in Teri Gram recorded "insufficient data". IMD forecast has similar dry weather conditions with dense smog across the National Capital Region (NCR) on Friday and Saturday, with windspeed remaining between 5 to 10 km per hour during the day. Gurugram recorded a minimum temperature of 10.4degC and a maximum of 17.3degC on Tuesday. Meanwhile, dense fog also forced the cancellation of at least 27 flights and delayed the operation of 500 more, officials aware of the matter said. The situation was compounded by a worsening AQI in the Capital, which by 7pm on Thursday, had reached 387, moving closer to the "severe" category by the hour. With the IMD issuing a yellow fog alert for Friday, the situation may worsen, experts said. The visibility dipped to 100 metres in the Capital on the day, impacting both railway and flight operations. "At 2.30am, visibility at Safdarjung was 300 metres and it was 500 metres at Palam. Visibility continued to dip and was 150 metres at Palam and 200 metres at Safdarjung at 6am - further dipping to 100 metres at both stations at around 6.30am," an IMD official said. Experts said that low winds, high moisture content in the air and high pollution levels created a thick smog, which kept a continuous haze through the day. "Flights were impacted, but this was not only down to low visibility here but also across the northern region. Visibility was zero at multiple other airports and so there has been an effect of flights being delayed at other airports too. Some flights were cancelled in advance too," an airport official, requesting anonymity, said. Data from flight tracking website Flightradar24 showed that over 500 flights stood delayed, while airport officials confirmed at least 27 flights were cancelled. This included 16 departures and 11 arrivals, including flights to Chandigarh and Lucknow, which recorded zero visibility. Officials said visibility dipped to zero at the Hindon airport, Agra airport, Kanpur airport, and Gorakhpur airport....