Achillea millefolium is highly variable and has been treated both as a single species with varieties and as multiple distinct species. A. millefolium is cosmopolitan throughout the Northern Hemisphere. In North America, A. millefolium is a complex of both native and introduced plants and their hybrids.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3232110/

http://globalresearchonline.net/journalcontents/volume9issue2/Article-022.pdf

https://www.herbal-supplement-resource.com/yarrow-herb.html

The Hungarian weather and climatic data sets are collected, managed and maintained by the Hungarian Meteorological Service. 

Hungary is situated between the 45°45'N and 48°35'N latitudes, about halfway between the Equator and the North Pole, in the temperate climatic zone according to the solar climatic classification. Its climate is very erratic. One of the main reasons for this is the fact that Hungary is situated in between 3 climatic zones: the oceanic climate with less varying temperature and more evenly dispersed precipitation; the continental climate with more extreme temperature and relatively moderate precipitation; also, a Mediterranean effect with dry weather in summer, and wet one in winter. For a shorter or longer period of time any of these types can become prevailing. Due to these reasons great differences can occur in the weather of the country, despite of its lower altitudes and relatively small extent. (https://www.met.hu/en/eghajlat/magyarorszag_eghajlata/altalanos_eghajlati_jellemzes/altalanos_leiras/)

Climate of the past century: https://www.met.hu/en/eghajlat/magyarorszag_eghajlata/eghajlati_visszatekinto/elmult_evszazad_idojarasa/

http://www.klimavalasz.hu/en/climate-change-hungary

https://www.tankonyvtar.hu/hu/tartalom/tamop425/0038_foldrajz_MikaJanos-eghajlat-EN/ch01s38.html