January in Koga averages a daily high of 10.1°C. Rain is rare — about 2.4 wet days and 25.1mm across the month. Generally workable, with some weather to plan around.
Across the year, the best time to visit Koga is April–May.
Based on KUMAGAYA, JA (30.2km), 1995–2024. 27 years of January data.