According to the pollen bulletin prepared by SPAIC, the pollen present in the air comes essentially from oak, pine and sycamore trees and nettle and parietaria herbs.

Forecasts up to April 6th, in Lisbon (Lisbon and Setúbal region), indicate that pollens are at very high levels, with a predominance of pollens from holm oak trees, oaks, sycamore and cypress and nettle and parietaria herbs.

In the interior regions of the country and in the Algarve, pollens from grasses and plantain begin to appear in the air and, gradually, to gain importance, and in the North, the concentrations are of birch pollen.

According to SPAIC, outdoor activities should be avoided when pollen concentrations are high.

Every week, the pollen bulletin publishes the levels of pollen in the atmosphere, collected by reading posts in various regions of the country.