[5] Most weather fronts originate in the Pacific Ocean, and travel east toward the Cascades where they are forced upward by the range (Orographic lift), causing them to drop their moisture in the form of rain or snowfall.

In the Crater Lake area, winter lasts eight months with an average snowfall of 41 feet (12.5 m) per year.

Hillman Peak was created when Mount Mazama, a large stratovolcano erupted violently approximately 7,700 years ago and formed on the caldera rim.

[4] Evidence suggests that the pre-eruption Hillman cone acted as a cleaver which was never entirely covered by glacial ice.

[8] According to the Global Volcanism Program (GVP), Hillman Peak is classified as a subfeature stratovolcano of Mount Mazama.