Based on the Köppen climate classification, Williams Peak is located in a subarctic climate zone with long, cold, snowy winters, and cool summers. Winds coming off the Gulf of Alaska are forced upwards by the Saint Elias Mountains (orographic lift), causing heavy precipitation in the form of rainfall and snowfall. Winter 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.