Juneau Basics. Juneau, the capital of Alaska and the second largest city in the state, is located on the Gastineau Channel, less than 100 miles from the US-Canadian border. The borough and city of Juneau is the second-largest in the United States by area--larger even than the state of Delaware.epending on the location in the city and borough, average annual rainfall ranges from 55 inches to over 90 inches, and the average annual snowfall at Juneau International Airport is 93 inches. June and July are the driest months, with an average of 16 days of rain.