New Delhi, Jan 12 (IANS): The air in Delhi-NCR turned 'severe' on Saturday due to calm winds and high humidity, authorities said, adding only rain could improve the situation to some extent.

The overall air quality index (AQI) of Delhi at 4 p.m. on Saturday was recorded at 423 (severe), on a scale of 0 to 500.

In the National Capital Region, Faridabad, Ghaziabad, Noida and Greater Noida also recorded 'severe' levels of particulate matter (PM)2.5.

System of Air Quality and Weather Forecasting And Research (SAFAR) however said that the air quality will improve by Tuesday even if rain does not occur, but it will still remain in the 'very poor' category.

"Other meteorological conditions are not favourable for dispersion of pollutants. Although foggy conditions are likely to reduce now," the agency said.

India Meteorological Department (IMD) has forecast light rains or thunderstorm on Saturday night and Sunday afternoon with the minimum temperature hovering around 9 degree Celsius.

It has also forecast a fall of 2-4 degree Celsius in the minimum temperature from Tuesday due to fresh western disturbance which would affect Western Himalayan region from Tuesday night. The maximum temperature will also drop from Sunday due to persistent clouding.