December in Sioux City averages a daily high of 1.5°C with nights around -9.3°C. Expect roughly 6.7 wet days totalling 26.2mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Sioux City is September–October.
Based on SIOUX CITY AIRPORT, IA US (12.2km), 1995–2024. 30 years of December data.