The west side of the North Cascades, including Hagan Mountain, receives significant precipitation, particularly during the winter months when snowfall is common.

[3] The temperate climate of the area, combined with its proximity to the Pacific Ocean, means that temperatures rarely drop below 0 °F (−18 °C) or rise above 80 °F (27 °C) in regions west of the Cascade Crest.

[3] However, it's important to note that maritime influence still plays a role, and snowfall in the area can be wet and heavy, resulting in a high risk of avalanches.

Geological events occurring many years ago created the diverse topography and drastic elevation changes over the Cascade Range leading to the various climate differences.

Uplift and faulting in combination with glaciation have been the dominant processes which have created the tall peaks and deep valleys of the North Cascades area.