The AccuWeather site forecasted that Hanoi would have harmful air on October 9, with the air quality index (AQI) remaining high at 112, while the ideal index for human health is between 0 and 50.
AccuWeather advised residents to refrain from venturing outside unless necessary.
Data released by Switzerland-based air quality monitor IQAir AirVisual showed that the AQI in Hanoi reached 174 on Monday morning, placing it at the top of the world’s most air-polluted cities list.
The National Centre for Hydrometeorological Forecasting has informed that Hanoi and other northern provinces will continue to be affected by spells of dry and sunny weather, low humidity, and a bit of mist in the mornings.
The weather pattern is forecast to remain over the coming days, and residents, especially children, pregnant women, and those suffering from respiratory diseases, are recommended to wear masks and glasses when going outside.