BACKGROUND - Canadian Rockies: Including Banff and Jasper National Parks - page 498

Ocean. Along the way it picks up the waters of the Kootenay River, which begins high in
Kootenay National Park and makes a lazy loop south through Montana and Idaho before
joining the Columbia at Castlegar, British Columbia, and the Kicking Horse River, which
flows down from the divides that form the borders of Yoho National Park. The Fraser
River, the longest river entirely within British Columbia, begins in the high reaches of
Mount Robson Provincial Park.
CLIMATE
More than any other factor, prevailing moisture-laden westerlies blowing across British
Columbia from the Pacific Ocean dictate the climate of the Canadian Rockies. The cold
heights of the mountain peaks wring the winds dry, making for clear, sunny skies in south-
ern Alberta; Calgary gets up to 350 hours of sunshine in June alone—good news, unless
you're a farmer. In winter, the dry winds blasting down the eastern slopes of the Rockies
can raise temperatures on the prairies by up to 40°C (104°F) in 24 hours. Called chinooks,
these desiccating blows are a phenomenon unique to Alberta.
Elevation and, to a lesser degree, latitude are two other factors affecting the climate
within the mountain ecosystem. Elevations vary from 800 meters (2,600 feet) above sea
level at Radium Hot Springs to 1,500 meters (4,920 feet) at Lake Louise to 3,954 meters
(12,970 feet) at the summit of Mount Robson. As a general rule, temperatures fall 5°C
(9°F) for every 1,000 meters (3,280 feet) of elevation gained. Another interesting phe-
nomenon occurring in the Canadian Rockies is the temperature inversion, in which a
layer of warm air sits on top of a cold air mass. During these inversions, high- and low-
country roles are reversed; prairie residents can be shivering and bundling up, while their
mountain fellows are sunning themselves in short sleeves.
The Seasons
Summer in the mountains is short, but the days are long. With up to 17 hours of daylight
around the summer solstice of June 21, this is an ideal time for travel and camping out. The
months on either side of summer are ideal for touring, especially September, when rainfall
is minimal. Winter is cold, but the skiing and snowboarding are fantastic.
January is usually the coldest month, when Banff's average temperature is -10°C
(14°F). In winter, extended spells of -30°C (-22°F) are not uncommon anywhere in the
mountains, and temperatures occasionally drop below -40°C (-40°F). The coldest temper-
ature recorded was -52°C (-62°F), in Lake Louise on January 25, 1950. Severe cold weath-