I concur that bigger meteogram would be a great help.
When I need to analyze charts in details I need to scale whole website to approx. 150%.
Generally information are presented superb.
Bug confirmed in incognito mode of Chrome after it was observed in standard mode so no cache is involved. All extensions disabled in incognito. (also checked in Edge)
Zoom levels 5,6,7,8 where displaying different temp. for Warszawa 3/6/3/6 degrees C.