Suomen ilmasto sopii Köppenin luokituksessa seuraavaan:
Moist, Severe Winter (D) Cimates
These climates are found poleward of the "C" climates. The "D" climates have longer, colder winters and greater annual range of temperature as compared with "C" climates. The boundary between C/D climates is where the coldest month averages below 32F. As you move from coastal areas toward the continental interior, winters become much colder and longer. Large landmasses are required to produce the "D" climates which is lacking on the southern hemisphere. Boreal Forest (assoc. with Cfa, Cfb, Dfa, Dfb) / Tiaga - the Boreal Forest occurs under a number of climatic regimes. The Boreal Forest is associated with climates having cool summers and cold winters. The trees are evergreen and are conifers. They have special adaptations to the severe climate. The air is dry here so plants need adaptations for temperature and precipitation fluctuations. Small leaves have thick cuticles. Trees are conical shaped to allow snow to fall off branches. The canopy is closed and is low to the ground. There is little ground cover. There are few species of trees in the Tiaga but you find extensive pure stands. Representative species include spruce, larch (tamarack), fir birch, pine.