Delhi saw its worst air for January in 2 years on Sunday, when AQI reached 440. The data from the Central Pollution Control Board showed the AQI at 447 on Sunday evening. The poor air has been blamed on the slow low-surface winds and moisture in the air, which is helping the pollutants to settle down. Delhi-NCR may also experience light rainfall on Monday and fog is expected to prevail in the morning and night.