Chandigarh, Dec. 27 -- As moderate fog continued in the city on Friday, the Air Quality Index (AQI) of Panchkula went up to 403 on Friday, bringing it into the severe category. Out of the 235 cities which were covered by the Central Pollution Control Board (CPCB) in their daily bulletin, Panchkula was the most polluted, leaving behind Delhi at 332. The AQI bulletin is prepared by taking the average of all monitoring stations in a city for their readings at 4 pm. The AQI readings are also taken as 24-hour averages and this bulletin presents a picture of the air quality through the day in a city. Panchkula has only one observatory, which the CPCB considers in its bulletin. It is located in Sector 6 at the Haryana State Pollution Control Board office. Even at 8 pm, the AQI of Panchkula was 410, which is considered severe. In the severe category, the air can affect healthy people and seriously impact those with existing diseases. After Panchkula, Baddi in Himachal Pradesh was the second most polluted city with an AQI of 394 while Greater Noida was the third with an AQI of 394. The AQI of Chandigarh increased from 186 on Thursday to 276 on Friday, bringing it back to the poor category. While this was expected to happen owing to foggy spells restarting in the city, dense fog is likely to continue in the coming days as per the India Meteorological Department (IMD). AQI between 201-300 is considered poor. On December 20, the AQI of the city was 302, which is classified as very poor. This was the highest it has gone this month. Chandigarh has three Continuous Ambient Air Quality Monitoring Stations (CAAQMS) in Sectors 22, 25 and 53, of which, the average is taken. At 8 pm, the AQI in Sector 22 was 269, in Sector 25 it was 274, and in Sector 53 it was 269. This paints a contrasting picture as just a few kilometres away, the AQI in Panchkula is in the severe category. Officials said that while Chandigarh is carrying out various processes to keep air pollution at bay, it could also be a technical glitch that has brought such a huge variation in the AQI at such a small distance. While fog continued in the city on Friday, the visibility dropped to 600 metres, making it a moderate fog day. There is an orange alert for dense fog on Saturday. Due to this, flight and train operations were affected. In all, 10 flights - seven departures and three arrivals- were cancelled at the Chandigarh International Airport due to visibility issues. The cancelled flights included those headed to Mumbai, Hyderabad, Lucknow, Kolkata, Hisar, Dharamshala and Pune. Of these, six flights were operated by IndiGo, while one was operated by Air India. The arrival cancellations involved flights coming from Pune, Delhi and Hyderabad, operated by IndiGo and Air India. The fog also affected railway operations, forcing loco-pilots to navigate at reduced speeds for safety. Among the worst affected was the Kalka Shatabdi Express from New Delhi. The premium train, scheduled to arrive at 10:59 am, was delayed by an hour and 15 minutes, finally reaching the platform at 12.14 PM. Long-distance services saw even more substantial disruptions. The Unchahar Express, traveling from Prayagraj, arrived four hours and 13 minutes behind schedule. Similarly, the Netaji Express recorded a delay of 2 hours and 47 minutes. Meanwhile the maximum temperature of the city rose from 17.4degC on Thursday to 20.7degC on Friday, 0.6 degrees above normal. The minimum temperature rose from 6.9degC on Thursday to 8.8degC on Friday, 1.8 degrees above normal. Over the next three days, the maximum temperature will remain between 18degC and 19degC while the minimum temperature will remain between 7degC and 8degC....