[3] It is located west of Suiattle Pass in the heart of the Glacier Peak Wilderness on land managed by Mount Baker-Snoqualmie National Forest.

[5] Plummer Mountain is located in the Cloudy Pass batholith, an intrusive formation that was formed approximately 20 million years ago, during the early miocene.

[5] As a result, valleys in the area are deep and U-shaped, and mountains tend to be rocky, with steep slopes and narrow summits.

As a result, the west side of the North Cascades experiences high precipitation, especially during the winter months in the form of snowfall.

[5] Due to its temperate climate and proximity to the Pacific Ocean, areas west of the Cascade Crest very rarely experience temperatures below 0 °F (−18 °C) or above 80 °F (27 °C).