December in Gary averages a daily high of 2.8°C with nights around -4.7°C. Expect roughly 12.5 wet days totalling 57.6mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Gary is May–September.
Based on INDIANA DUNES NATIONAL PARK, IN US (21.9km), 1995–2024. 26 years of December data.