January in Castle Rock averages a daily high of 7.7°C with nights around -8°C. Expect roughly 4.8 wet days totalling 15.4mm. Demanding conditions — pack for it and plan indoor options.
Across the year, the best time to visit Castle Rock is May–June.
Based on CASTLE ROCK, CO US (1.7km), 1995–2024. 27 years of January data.