Delhi witnesses poor air quality for a major part of the year. (PTI file photo)

Residents of Delhi on Sunday breathed the cleanest air of the year so far, thanks to widespread rainfall in the National Capital Region over the past few days, officials said.

According to the Central Pollution Control Board, the air quality index (AQI) in Delhi on Sunday was recorded at 47, which falls in the "good" category.

The AQI improved from 49 on Saturday, the CPCB said. An AQI between 0 to 50 is considered "good" air quality.

"Sunday's was the best AQI this year so far," an official said, adding the air quality will remain in the "good" category for the next three days.

For major part of the year, the city witnesses poor air quality.

The Centre-run System of Air Quality and Weather Forecasting (SAFAR) attributed the improved air quality to widespread rainfall in and around the NCR.

"Increased west to North rainfall activity in association with the interaction between western disturbance and monsoon low is ensuring longest spell of best air quality of the year.

"It will continue for today also. Fairly widespread to widespread rainfall and isolated heavy rainfalls are also expected. Delhi Air quality is predicted to be in good category for next three days," it said.

Delhi-NCR has received widespread intermittent rainfall over the past few days. Delhi received 1.4 mm rainfall from 8.30 am to 5.30 pm on Saturday, while in 24 hours ending 8.30 am on Saturday it received 7.3 mm rainfall.

Some parts of the city received rains on Friday and Thursday as well.

An AQI between 51 and 100 is considered "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor'', and 401 and 500 "severe".

The level of PM 2.5 (particles in the air with a diameter of less than 2.5 micrometre) was recorded at 26 and the PM 10 level was recorded at 17 on Sunday, the SAFAR said.