The actual northernmost French (the Republic) community is in Saint-Pierre-et-Miquelon, which is funnily enough just next to Quebec! it's an overseas territory and they use the Euro as their currency.
Even Paris is north of Saint-Pierre-et-Miquelon.
Otherwise maybe the chart would show quite a bit more "latitudinal population variation" with the southernmost significant populated place being 20° south of the equator.