Question 1

What is the weather like in Leiden by month?

Accepted Answer

No monthly climate normals are on file for Leiden.

Question 2

When is air quality worst in Leiden?

Accepted Answer

March carries the highest modelled PM2.5 of the year at about 16 µg/m³. The WHO 2021 annual guideline is 5 µg/m³. These are model values, not station readings.

Leiden weather by month