This paper presents the course of the pollen season of ragweed (Ambrosia) in selected cities of Poland (Lublin, Warsaw, Szczecin, Zielona Gora, Wroclaw and Bialystok) in 2024. The ragweed pollen grains are known as very potent aeroallergens, often noted to enter into cross reactions. This pollen is a common cause of pollinosis in North America. In Europe ragweed is an introduced species in the middle of an ongoing invasion event and, therefore, represents a case of a human population being exposed to increasing concentrations of this allergen. Measurements were performed by the volumetric method (Burkard and Lanzoni pollen samplers). Pollen season was defined as the period in which 98% of the annual total catch occurred. Seasonal Pollen Index (SPI) was estimated as the annual sum of daily average pollen concentrations. The pollen season of Ambrosia in 2024 started first in Wroclaw, on the 12th of August, then in Lublin and Warsaw, on the 15th and 16th of August (about 1–2 weeks earlier than in the other cities). This pollen season lasted between the 22nd of September and the 27th of September. The differences of pollen seasons durations were clear (from 27 to 44 days). The highest airborne concentration of 174 pollen grains/m3 was noted in Lublin on the 4th of September. The maximum values of seasonal pollen count occurred between 4th and 17th of September, only in Wrocław 28th of August. The highest ragweed pollen allergen hazard occurred in 2024 in Warsaw and lasted 23 days and in Lublin – 22 days and was high. So far, in various years in Poland, this threat lasted less than 10 days.