Hanoi's air quality has returned to normal after several days of reaching levels dangerously high for health.

On the evening of December 13th, Hanoi's air unexpectedly turned "green" again after several consecutive days of reaching "purple" levels (harmful to health), and even for the first time reached "brown" levels (extremely harmful to health).

The sky over Hanoi, as seen from the Tay Son MIPEC area, brightened at 4:06 PM on December 13th, and the air was fresher after many days of thick dust. (Photo: THU HA)

The rain all day today (December 13th) has brought clear skies back to Hanoi after a series of consecutive days from the beginning of the month reaching record highs, exceeding levels of air quality that could be particularly harmful to human health. The peak was last night (December 12th) at 9:18 PM, when the air quality reached the "brown" level with an AQI of 309, ranking among the worst air pollution levels in the world .

The air quality index first reached the "brown" level at 9:18 PM on December 12, 2025.

Previously, on December 12th, Hanoi's air quality consistently remained at the "purple" level, with indicators continuously ranking among the top 5 cities in the world.

Early on the morning of December 13th, many Hanoi residents were surprised by the thick fog covering the sky, especially due to the cold rain. However, the continuous rain from early morning until afternoon somewhat washed away the thick layer of dust that had covered Hanoi's sky in recent days, so that at 6:01 PM on December 13th, Hanoi's air quality returned to "green" with an AQI index of 50, ranking 87th in the world, temporarily escaping the vicious cycle of recent air pollution.

The air quality index ranks it 87th among cities worldwide, placing it at the "green" level (safe for health).

The weather in Hanoi changes hour by hour throughout the day:

The Hanoi sky as seen from the HANDICO office building on Pham Hung Street at 7:25 AM on December 13th. (Photo: HNV)

The Hanoi sky as seen from the Vinhomes Times City Minh Khai urban area at 9:00 AM on December 13th. (Photo: DO HA)

The Hanoi sky as seen from the apartment building at 71 Nguyen Chi Thanh at 11:30 AM. (Photo: HNV)

The Hanoi sky as seen from the apartment building at 71 Nguyen Chi Thanh at 12:15 PM. (Photo: HNV)

No longer "hazy," the city looks clearer at 4 PM. (Photo: TRAN KHANG)

The sky over Hanoi was clearer at 4:10 PM. (Photo: THU HA)

PV

Source: https://nhandan.vn/khong-khi-ha-noi-xanh-lai-sau-nhieu-ngay-dat-nguong-dac-biet-nguy-hai-cho-suc-khoe-post930072.html