Based on the Köppen climate classification, Mount Adair is located in a subarctic climate zone with long, cold, snowy winters, and mild summers. Temperatures can drop below −20 °C with wind chill factors below −30 °C. This climate supports a spruce and hemlock forest on the lower slopes.
^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.
East aspect of Mount Adair reflected in Kenai Lake