BACKGROUND - Canadian Rockies: Including Banff and Jasper National Parks - page 499

er is often accompanied by sunshine; the cold is a dry cold, unlike the damp cold experien-
ced in coastal regions. Cold temperatures and snow can be expected through mid-March.
Although March, April, and May are, more or less, the official months of spring, snow
often falls in May, many lakes may remain frozen until June, and snow cover on higher
mountain hiking trails remains until early July. During this period of the year, the moun-
tains are often affected by low-pressure weather patterns from the southeast, creating con-
tinuous days of rain, especially in the south.
Things warm up in summer. July is the hottest month, with Banff, Jasper, and Can-
more's average daytime temperature topping out above 23°C (73°F) and Radium Hot
Springs and Golden enjoying average daytime highs of 29°C (84°F) and 27°C (81°F), re-
spectively. On hot days, the temperature can hit 30°C (86°F) along lower-elevation val-
leys. Again, because of the dryness of the air, these temperatures are more bearable here
than in coastal regions experiencing the same temperatures.
By late September, the mountain air begins to have a distinct chill. October brings the
highest temperature variations of the year; the thermometer can hit 30°C (86°F) but also
dip as low as -20°C (-4°F). Mild weather can continue until early December, but generally
the first snow falls in October, and by mid-November winter has set in.
CHINOOK WINDS
On many days in the dead of winter, a distinctive arch of clouds forms in the sky
over the southwestern corner of Alberta as a wind peculiar to the Canadian Rockies
swoops down over the mountains. The warm wind, known as a chinook (snow eat-
er), can raise temperatures by up to 20°C (68°F) in an hour and up to 40°C (104°F)
in a 24-hour period. The wind's effect on the snowpack is legendary. One story tells
of a backcountry skier who spent the better part of a day traversing to the summit
of a snow-clad peak on the front range of the Canadian Rockies. As he rested and
contemplated skiing down, he realized that the slope had become completely bare!
Chinooks originate over the Pacific Ocean when warm, moist air is pushed east-
ward by prevailing westerlies. The air pressure of these winds is less than at lower
elevations, and, therefore, as the air moves down the front ranges of the Canadi-
an Rockies, it is subjected to increased pressure. This increasing of the air pressure
warms the winds, which then fan out across the foothills and prairies. The “chinook