The national Capital's air quality improved on Wednesday due to a favourable wind speed with the 24-hour average air quality index (AQI) reading 237 at 4 pm.
Neighbouring Faridabad (188), Ghaziabad (229), Greater Noida (154), Gurgaon (185) and Noida (186) also recorded improvement in their air quality.
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'.
The Ministry of Earth Sciences' air quality forecast agency SAFAR said the improvement in the air quality was "higher than expected, implying that (air pollution) control measures are yielding results".
Moderate wind speed is likely to increase ventilation over the next four days, it said.
However, a gradual decrease in temperatures will lead to a drop in the mixing height -- the vertical height in which pollutants are suspended in the air -- in the coming days, it said.
The mixing height reduces on cold days with calm wind speed.
Mahesh Palawat, Vice President (Meteorology and Climate Change), Skymet Weather, said moderate wind speed will help improve the air quality further.
Cold northwesterly wind will commence from Friday after a Western Disturbance affecting the hilly region recedes, causing the minimum temperature to drop by two to three degrees Celsius, he said.