Spring comes to the valley bottoms in mid-April and reaches the high country by mid-June. Summer days are long, but the summer season is short. July is the warmest month with a mean daily maximum temperature of 22.5 degrees Celsius. September and October bring fall colours, clear skies and cooler temperatures. The long winter season is varied with periods of cold stormy weather that can quickly change to a mild chinook wind. January is the coldest month with a mean maximum temperature of -9.4 degrees Celsius.
In mountainous terrain, a number of factors contribute to climate and weather patterns and create a variety of micro-climates. These factors include elevation, latitude, prevailing winds, alignment of valleys, shading from mountains, and winds from the glaciers.
Altitude has a great impact on the local climate; the higher the elevation, the colder the temperature. Generally, a loss of 1.7 degrees Celsius can be expected with every 300 metres of elevation gained.
The winds from the southwest also have a significant influence on local weather. Although the Pacific Ocean lies several mountain ranges away, winds from the sea bring warm air and moisture to the mountains. Most of the moisture is dropped from these systems before they reach the eastern slopes of the Rockies.