The northern limits for Québec of the dispersion and breeding ranges of the common green darner (Anax junius) were updated during work for the Migratory Dragonfly Partnership. The new limits presented are based on scientific literature and previously unpublished data from the Québec Dragonfly Atlas Initiative. Each year, the first adults arriving from the United States of America are reported from the lowlands of the Outaouais and St. Lawrence rivers in May, and exceptionally in late April. The species is also occasionally reported from the Laurentian and Appalachian foothills, and from inhabited areas along the shores of the Estuary and the Gulf of the St. Lawrence River between the 47th and 50th parallels north. In the extreme southern part of Québec, the emergence of overwintering populations is occasionally observed in June or early July. In the temperate deciduous region of the province, the emergence of summer populations regularly occurs from mid-August to early October. In the temperate mixed region found in the Témiscouata area, emergences may occur and this might also be the case in the Saguenay–Lac-Saint-Jean area. According to the climate model proposed by Gérardin and McKenney (2001), the northern limit of the breeding range of the common green darner could reach the 49th parallel, following the 15.7°C isotherm for the warmest three summer months. Therefore, it seems unlikely that this species is able to complete its life cycle in boreal regions, such as on Anticosti Island. Climate change could be marked by an earlier arrival of immigrant adults in the spring, and by an increase in the frequency of the emergence of overwintering and summer populations of naiads.