The aim of the study was to compare the birch pollen seasons in selected 12 cities in Poland in 2020. The volumetric method of sampling was used to collect pollen samples. The estimation of the seasonal parameters was based on descriptive statistics. The clear differences among SPIn values at all sites were recorded. The lowest value was recorded in Bialystok (1.863 pollen/m3), whereas the highest one in Lublin (16.253 pollen/m3). The thermal conditions in the north-eastern part of Poland were the least favourable for birch pollen seasons.