Based on the Köppen climate classification, Mount Castner is located in a subarctic climate zone with long, cold, snowy winters, and mild summers. 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. Temperatures can drop below −20 °C with wind chill factors below −30 °C. This climate supports the Meares and Yale Glaciers surrounding this mountain. The months May through June offer the most favorable weather for climbing or viewing.
Mt. Castner in lower left corner of frame. Mount Grosvenor and Meares Glacier to right
^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.