Altitude is a major factor in Banff's climate. Temperatures are vastly different between the town of Banff at 1,400 meters above sea level and the park's highest peak, Mount Forbes, rising to 3,600 meters. At all times of the year, there is a drop of 1 degree C for every 200 meters. Daily low temperatures in Banff average minus 15 degrees C in January while in Lake Louise, which is 130 meters higher, the corresponding temperature is minus 21.5 degrees C. Snowfalls during the same month average 38 centimeters in Banff and 63 centimeters in Lake Louise. At higher elevations in the park, 1,000 centimeters have been recorded. Mountaintops retain snow year round and passes might be closed until June.
Wind has the largest effect on the area's climate and weather patterns. The prevailing winds from the west, called the chinook winds, bring warm air and moisture across British Columbia and Alberta. As they reach the western slopes of the Rockies the moist air rises and cools, causing high precipitation. It is dryer as it moves across the Rockies and becomes warmer as it descends the eastern slopes. This low humidity makes the colder temperatures of winter and occasional hot spells in summer more comfortable than it would be otherwise.
Latitude also plays a role. At 51 degrees north, the sun's rays hit the ground at an angle year round, decreasing their warming effect. The park sees as little as eight hours of sunlight in December contributing to the cold winters and temperatures soon begin a warming trend that continues into summer when at the end of June there is as much as 16 hours of light.
Winter is the longest season, with regular snowfalls lasting from November through March. Temperatures average minus 12 degrees C in Banff during these months with occasional cold snaps of minus 30 degrees C in December.
Although snows continue into spring, rain becomes more prominent in April and temperatures moderate, rising to an average of 18 degrees C in June.
Summer, lasting from July to August, and autumn, in September to October, are the shortest seasons. Banff routinely experiences days of 22 degrees C in July. It registered a record high of 34.5 degrees C.
The fall months see falling temperatures but rarely drop below freezing and daily highs range from 10 to 16 degrees C. The first snows of the year arrive in September but are light and usually melt quickly.
Average Temperatures (Celsius)
Banff Lake Louise
January
High -5.3 -7.5
Low -14.9 -21.4
April
High 9.0 7.1
Low -2.8 -6.7
July
High 22.1 20.4
Low 7.4 3.6
October
High 10.1 7.9
Low -1.1 -5.5
