December in Casper averages a daily high of 3.5°C with nights around -7.6°C. Expect roughly 4.5 wet days totalling 17.7mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Casper is June.
Based on CASPER WASTE WATER TREATMENT PLANT, WY US (1.8km), 1995–2024. 22 years of December data.