December in Round Rock averages a daily high of 16.9°C with nights around 5.1°C. Expect roughly 7.7 wet days totalling 52.3mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Round Rock is February–April.
Based on AUSTIN GREAT HILLS, TX US (13.4km), 1995–2024. 17 years of December data.