Based on the Köppen climate classification, Mount Tantalus is located in the marine west coast climate zone of western North America. Most weather fronts originate in the Pacific Ocean, and travel east toward the Coast Mountains where they are forced upward by the range (Orographic lift), causing them to drop their moisture in the form of rain or snowfall. As a result, the Coast Mountains experience high precipitation, especially during the winter months in the form of snowfall. Temperatures can drop below −20 °C with wind chill factors below −30 °C.
^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.
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