boreal zone

Boreal \Bo"re*al\, a. [L. borealis: cf. F. bor['e]al. See
   {Boreas}.]
   1. Northern; pertaining to the north, or to the north wind;
      as, a boreal bird; a boreal blast.
      [1913 Webster]

            So from their own clear north in radiant streams,
            Bright over Europe bursts the boreal morn.
                                                  --Thomson.
      [1913 Webster]

   2. (Biogeography) Designating or pertaining to a terrestrial
      division consisting of the northern and mountainous parts
      of both the Old and the New World; -- equivalent to the
      Holarctic region exclusive of the Transition, Sonoran, and
      corresponding areas. The term is used by American authors
      and applied by them chiefly to the Nearctic subregion. The
      Boreal region includes approximately all of North and
      Central America in which the mean temperature of the
      hottest season does not exceed 18[deg] C. (= 64.4[deg]
      F.). Its subdivisions are the Arctic zone and

   {Boreal zone}, the latter including the area between the
      Arctic and Transition zones.
      [Webster 1913 Suppl.]