Delhi's air quality was also recorded in very poor category on Thursday.
The national capital was engulfed in a blanket of fog on Thursday morning with the weather office predicting light rain and shallow fog on Friday even as the city's maximum temperature settled at 19.1 degrees Celsius, two notches below the season's average.
According to the weather office, moderate fog was witnessed at Safdarjung observatory, considered the official marker for the city, and visibility there was 400 metre. However, dense fog conditions prevailed at Palam observatory where visibility dropped to 50 metres on Thursday morning.
“There will be partly cloudy sky with possibility of light rain or drizzle towards evening on Friday. There will be shallow fog in the morning,” the India Meteorological Department (IMD) predicted.
The minimum temperature on Thursday was recorded at 9.8 degrees Celsius, three notches above the season's average, the IMD said.
Meanwhile, foggy conditions led to delay in arrival of around a dozen Delhi-bound trains, railway officials said.
The relative humidity at 5.30 pm on Thursday was 81 per cent, the weather office said.
Delhi's air quality was also recorded in very poor category on Thursday as the AQI value in 24 hours AQI bulletin at 4 pm on Thursday was 387, the Central Pollution Control Board (CPCB) data showed.
The AQIs of its neighbouring cities -- Ghaziabad (375), Gurugram (324), Greater Noida (320) and Noida (357) -- were also recorded in the very poor category. Air quality in Faridabad was in severe category with AQI at 4 pm recorded at 412.
An AQI between zero and 50 is considered good, 51 and 100 satisfactory, 101 and 200 moderate, 201 and 300 poor, between 301 and 400 very poor, and 401 and 500 severe.