Chandigarh, Dec. 6 -- The city's air quality index (AQI) has once again turned poor due to the drop in temperature. Some relief from the cold is expected over the weekend as a feeble Western Disturbance (WD) will affect the region. As per the daily AQI bulletin, released by the Central Pollution Control Board (CPCB), the AQI of Chandigarh on Friday was 213, which is considered poor. This is calculated by taking the average of all three Continuous Ambient Air Quality Monitoring Stations (CAAQMS) situated in the city. The readings taken at 4 pm are used for this. As per the CPCB, AQI between 201-300 is considered poor and can cause breathing discomfort to most people on prolonged exposure. This comes after around a month of moderate to satisfactory air quality. In comparison, the AQI of Panchkula on Friday was satisfactory at 97 while the AQI of Delhi was very poor at 327. On Thursday, the AQI of Chandigarh was 187 while that of Panchkula was 96 and Delhi was 304. IMD Chandigarh director Surender Paul said the poor AQI is a result of temperature inversion. "Sliding temperature leads to concentration of pollutants increasing and a drop in air quality," he said. On why the air quality was satisfactory over the last month, Paul said, "The cold North Westerly winds blowing in the city over the past month kept the pollutants from collecting. However, with a fresh WD affecting the region, these winds have also been disrupted. While no rain is expected, the WD is likely to bring warmer Westerly winds to the region." Meanwhile, the minimum temperature of the city dropped from 6.3degC on Thursday to 6.1degC on Friday, 4.5 degrees below normal. This is the second day this season with cold wave conditions. Earlier on Wednesday, the minimum temperature had dropped to 5.4degC. As per the IMD, for this region, a cold wave is declared when the minimum temperature is below 10degC and falls between 4.5 to 6.4 degrees below normal. The maximum temperature rose from 22.3degC on Thursday to 23.9degC on Friday, but was still 1.5degC below normal. Over the next three days, the maximum temperature will remain between 25degC and 26degC while the minimum temperature will remain between 8degC and 9degC....