According to some authors, ash pollen has strong allergenic properties. In Europe the allergenic significance of this pollen has been poorly studied as the amounts of ash pollen in the air are low. However, in Poland we are more and more often observing ash pollen seasons with the total annual pollen sum exceeding 1000 grains. In 2023, it was found in Cracow and Łódź. This study compares the ash pollen seasons in Bialystok, Bydgoszcz, Cracow, Kielce, Piotrkow Trybunalski, Opole, Olsztyn, Szczecin, Lodz, Wroclaw, Zielona Gora, Warsaw and Lublin in 2023. The investigations were carried out using the volumetric method (Hirst type pollen sampler). Seasonal pollen index (SPI) was estimated as the sum of daily average pollen concentrations in the given season. The ash pollination is mainly observed in April. Diagnosis of ash pollen allergy is made difficult due to an overlapping pollination period with Betulaceae and some cross-reactivity with allergens from birch, and even privet and olive. It is not clear whether ash pollen is a primary cause of sensitization or whether it is implicated through cross-sensitization to other pollens. In 2023 the pollen season of ash started first in Kielce and Opole, on the March 11th and 13th. At the latest, a pollen season ended in Bialystok, on the May 12th. The differences of pollen seasons duration were very considerable, from 23 to 57 days. The highest airborne concentration of 530 (!) pollen grains/m3 was noted in Cracow on the April 3rd. The peak values of seasonal pollen count in Polish cities occurred between April 3rd and 24th, most often between April 17th and 24th. The highest ash pollen allergen hazard occurred in 2023 in Cracow and Lodz, and was at least 2–3 times higher than in other cities. The highest variability in the analysed seasons was found in the peak value and annual total.