September in Rijeka averages a daily high of 24.3°C with nights around 15.6°C. Expect roughly 9.6 wet days totalling 195.7mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Rijeka is May–June.
Based on RIJEKA, HR (0.9km), 1995–2024. 28 years of September data.