<p>Cold conditions persisted in the national capital as the minimum temperature remained below five degrees Celsius for the fourth consecutive day on Saturday, the India Meteorological Department said.</p>.<p>The Safdarjung Observatory, which provides representative data for the city, recorded a minimum of 4.4 degrees Celsius, three notches below normal.</p>.<p>"Shallow" fog reduced visibility to 1000 meters at Safdarjung and 800 meters in the Palam area, Kuldeep Srivastava, the head of the IMD's regional forecasting centre, said. </p>.<p>According to the weather department, "very dense" fog is when visibility is between 0 and 50 meters, 51 and 200 is "dense", 201 and 500 "moderate", and 501 and 1,000 "shallow". </p>.<p>The mercury is likely to increase slightly on Sunday and Monday under the influence of a fresh Western Disturbance affecting the upper reaches of the Himalayas. Moderate fog is likely during this period, Srivastava said.</p>.<p>Cold wave conditions will return December 29 onwards, he said.</p>.<p>For the plains, the IMD declares a cold wave when the minimum temperature is 10 degrees Celsius or below and is 4.5 notches less than normal.</p>.<p>Delhi's air quality improved slightly but it was still "very poor".</p>.<p>The city's air quality index (AQI) was 324 at 9 am. The 24-hour average AQI was 357 on Friday, 423 on Thursday, 433 on Wednesday and 418 on Tuesday.</p>.<p>An AQI between zero and 50 is considered "good", 51 and 100 "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor", and 401 and 500 "severe".</p>.<p>A marginal improvement is predicted by Sunday as wind speed picks up under the influence of the WD, Srivastava said.</p>.<p>However, he said, the air quality will dip again, starting Monday, due to predicted high humidity, low wind speed and temperatures.</p>
<p>Cold conditions persisted in the national capital as the minimum temperature remained below five degrees Celsius for the fourth consecutive day on Saturday, the India Meteorological Department said.</p>.<p>The Safdarjung Observatory, which provides representative data for the city, recorded a minimum of 4.4 degrees Celsius, three notches below normal.</p>.<p>"Shallow" fog reduced visibility to 1000 meters at Safdarjung and 800 meters in the Palam area, Kuldeep Srivastava, the head of the IMD's regional forecasting centre, said. </p>.<p>According to the weather department, "very dense" fog is when visibility is between 0 and 50 meters, 51 and 200 is "dense", 201 and 500 "moderate", and 501 and 1,000 "shallow". </p>.<p>The mercury is likely to increase slightly on Sunday and Monday under the influence of a fresh Western Disturbance affecting the upper reaches of the Himalayas. Moderate fog is likely during this period, Srivastava said.</p>.<p>Cold wave conditions will return December 29 onwards, he said.</p>.<p>For the plains, the IMD declares a cold wave when the minimum temperature is 10 degrees Celsius or below and is 4.5 notches less than normal.</p>.<p>Delhi's air quality improved slightly but it was still "very poor".</p>.<p>The city's air quality index (AQI) was 324 at 9 am. The 24-hour average AQI was 357 on Friday, 423 on Thursday, 433 on Wednesday and 418 on Tuesday.</p>.<p>An AQI between zero and 50 is considered "good", 51 and 100 "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor", and 401 and 500 "severe".</p>.<p>A marginal improvement is predicted by Sunday as wind speed picks up under the influence of the WD, Srivastava said.</p>.<p>However, he said, the air quality will dip again, starting Monday, due to predicted high humidity, low wind speed and temperatures.</p>