Delhi's air quality deteriorated sharply on Sunday, with the Air Quality Index (AQI) rising to 261, placing it in the 'Poor' category, just five days after the city recorded its cleanest air of 2026.

According to CAQM, the unexpected rise in pollution was a result of cross-border winds that were bringing substantial dust particles from Afghanistan, Iran, and Pakistan, into Northwestern India. The dusty winds played a very significant role in raising the particulate matter concentration in the national capital, thereby deteriorating its air quality rapidly.

The AQI in the city was measured at 59 on Wednesday, which came under the category of 'Satisfactory'. It represented the lowest AQI of the year in Delhi up till now. Nevertheless, the effect of the dust storm that was coming towards the city made pollution increase drastically over the next few days.

AQI from 201 to 300 comes under 'Poor'. This means that there might be some difficulties with breathing experienced by those people who have breathing problems due to prolonged exposure.

As per the CAQM, the degradation was mostly attributed to the natural phenomenon prevailing in the weather, and not emissions in Delhi NCR. The dust brought in through long distance transportation from nearby regions led to low visibility and high concentration of coarse particle matter in the Delhi NCR region.

It has been pointed out that the occurrence of dust intrusion phenomena is frequent in the summers and during the monsoon transitional season, due to the strong western winds that blow the desert dust in northern India.

The latest AQI reading is the highest recorded in Delhi since April 17, highlighting how quickly weather conditions can influence pollution levels despite recent improvements in the city's air quality.