"Pollen" is plural. The pollen calendar is dominated by six species the Open-Meteo air-quality API reports separately: alder, birch, grass, mugwort, olive, and ragweed. Each peaks in a different window and each provokes a different fraction of the allergic population.
Alder peaks in late winter through early spring (February-April in temperate climates), often the first allergen to drift into homes after winter. Birch follows in April-May, particularly dominant in northern Europe and the U.S. Northeast. Both are tree pollens: heavy, falling fast, but produced in enormous quantities.
Grass peaks in late spring to early summer (May-July in temperate North America, extending later at higher latitudes). It is the single most prevalent allergen worldwide. Mugwort (Artemisia) is a European late-summer dominant; olive is the Mediterranean spring allergen. Neither is significant in most of North America. Ragweed is the North American late-summer/early-fall driver: peak August through first frost, capable of traveling hundreds of kilometers on wind, and producing some of the largest pollen-count days of any species. EPA documents ragweed season lengthening by 21+ days at northern U.S. latitudes over the past 30 years.
The dashboard pulls all six species from Open-Meteo and shows whichever ones are currently elevated for your latitude. When pollen of any species is high outdoors and your indoor PM10 rises in correlation, the dashboard suggests closing windows and running filtration: the same intervention regardless of species, but the species identification helps users learn their own sensitivities over time.
References
- AAAAI - Pollen allergy guide www.aaaai.org
- Pollen.com - National allergy forecast pollen.com
- Open-Meteo - Air Quality API documentation open-meteo.com
- EPA - Climate change indicators: ragweed pollen season www.epa.gov
