It is set midway between Girdwood and Whittier, with the Portage Glacier Highway and Alaska Railroad traversing the southern base of the mountain.

Precipitation runoff from the peak drains into Turnagain Arm via Portage Creek and Twentymile River.

Based on the Köppen climate classification, Portage Peak is located in a subarctic climate zone with long, cold, snowy winters, and mild summers.

[3] Weather systems coming off the Gulf of Alaska are forced upwards by the Chugach Mountains (orographic lift), causing heavy precipitation in the form of rainfall and snowfall.

The months May through June offer the most favorable weather for climbing or viewing.