Which months, in practice
| Period | Typical AQI quoted | What it means |
|---|---|---|
| December to February | 150 to 250 and more | Unhealthy to very unhealthy, grey skies common |
| March to May | 100 to 180 | Moderate to unhealthy |
| June to August | 60 to 100 | The cleanest, but hot, humid and rainy |
| September to November | 80 to 150 | Rising from October |
Another source says northern Vietnam has its highest levels from October to March. The orders of magnitude agree: winter is the risky time. To choose your date in general, read the best time to visit Hanoi.
What to do
- Track the AQI: check an air-quality app (for example IQAir) in the morning before planning.
- Mask: if the AQI is above about 150, an N95, KN95 or FFP2 filtering mask is more useful than a surgical mask.
- Sensitive people (asthma, children, older travellers): avoid long bike or scooter outings on red days; see also medical help in Hanoi.
- Indoor plan B: water puppet show (see the puppet theatre), museums, a cooking class, a spa or shopping malls.
- Day trips: Ninh Binh, Cat Ba or Ha Long often have more breathable air than central Hanoi, but fog can spoil the views; see Ha Long in winter.
FAQ
Is Hanoi dangerous for your health?
A short stay is not a major risk for most travellers, but sensitive people should take precautions on high-AQI days.
Which month has the best air?
Summer (June to August) is cleanest, but it is hot and rainy.
Which mask should I choose?
A well-fitted N95, KN95 or FFP2.
