When we visited Glacier Nation Park (US) in early July, Logan Pass was closed.
Good luck!
US
http://www.nps.gov/glac/planyourvisit/hours.htm
http://www.nps.gov/glac/planyourvisit/weather.htm
or Canada
http://www.banffnationalpark.com/howto/banff-national-park-visitor-information.html