Based on the Köppen climate classification, Porphyry Mountain is located in a subarctic climate zone with long, cold, snowy winters, and cool summers. Weather systems coming off the Gulf of Alaska are forced upwards by the Wrangell Mountains (orographic lift), causing heavy precipitation in the form of rainfall and snowfall. Temperatures can drop below −20 °C with wind chill factors below −30 °C. The months May through June offer the most favorable weather for viewing and climbing.
^Peel, M. C.; Finlayson, B. L.; McMahon, T. A. (2007). "Updated world map of the Köppen−Geiger climate classification". Hydrol. Earth Syst. Sci. 11. ISSN1027-5606.
Porphyry Mountain and National Creek Rock Glacier from Donoho Basin