The weather climate in Glacier National Park is very unique to many other places.  Glacier National Park does not have one specific climate but is comprised of many microclimates.  This is because of the rapid changes in elevation and its location on the North American Continent.  The park falls along the Atlantic-Pacific Divide and is also separated into eastern and western landscapes by the Rocky Mountains (Continental Divide).

(The Red Line down Montana, where the park is located, is the continental divide separating the park into Eastern and Western sides and influencing the climate change between the two sides.)

Because of this the Western Side of the park tends to be warmer and wetter in relation to the Alaskan Current and the Eastern Side tends to be drier, colder, and windier because of the air current coming from the great plains. 

One of the reasons that the western side of the park receives warmer air currents is because of Air Mass Movement.  The Alaskan current is sending oceanic air masses. Oceanic Air masses tend to be warmer and wetter then continental Air masses.  The Eastern side of the park tends to be colder and dryer because of the continental air mass movement from the great plains just east of the park.  

(It is the mP air current coming from the pacific ocean that creates the wetter and warmer climate on the West side of the park)

This park is composed of many different changes in elevations.  This creates pockets or microclimates based on the different processes the Earth uses to cool and heat different  areas.  It is because of this that the park can experience extreme climate changes.  In fact Glacier National Park holds the world record for the biggest and fastest change in temperature.  In 1916 on the night of January 23-24 the temperature dropped 112 degrees F.  It dropped from 44 F to Negative 56 F.  One of the self regulating processes that lead to such dramatic climate change is related to the processes of global scale circulation.  Global scale circulation sends warmer air upward from lower latitudes to higher latitudes and colder air from higher latitudes to lower latitudes. 

(This topographical map shows the extreme changes in elevation throughout areas of the park.)

Because the Park is made up of many mountains and valleys the latitude of the park is very rarely consistent and the Global scale circulation tends to overlap creating areas of extreme temperatures, both hot and cold depending on the changes in latitude and the season.     

References

http://www.glacier-national-park-travel-guide.com/glacier-national-park-weather.html