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Two major climatic zones,
the arctic and sub arctic, divide the
Northwest Territories at the tree line into
two almost equal parts. While both regions
have extremely cold and long winters, the
arctic climate has a shorter and cooler
summer, with the average monthly temperature
remaining below 10° C (50° F). The sub
arctic climate has a longer and warmer
summer, with at least three months having
average monthly temperatures exceeding 10°
C. During the long, cold winter,
temperatures often reach -50° C (-60° F) in
both climatic zones. Arctic blizzards and
whiteouts frequently punctuate the winter
weather. An arctic blizzard is a fierce
snowstorm with intensely cold and strong
wind. Within the Arctic, “whiteout” weather
conditions can occur, causing a loss of
depth perception. Under these conditions,
pilots have great difficulty landing an
aircraft.
The arctic climate is the
most northerly climate in the world. It lies
north of the tree line and is associated
with tundra vegetation. In these frigid
lands, summer may bring only a few warm
days. With such a short summer, tree growth
is not possible. Precipitation is low, often
less than 100 mm (4 in), and most occurs in
the summer.
A sub arctic climate
prevails over the remainder of the Northwest
Territories, particularly in the Mackenzie
Valley. This climate is characterized by a
much longer and warmer summer. While
precipitation is low and summers are still
relatively short, sufficient moisture (300
mm/12 in) and warmth make it possible for
trees to grow. The sub arctic climate is
associated with the boreal forest, a
northern coniferous forest consisting of
pine, spruce, fir, and larch.
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