Gulangyu is extremely crowded on national holidays and most weekends from April through October. The island receives millions of visitors per year — recent estimates put it among the most visited UNESCO sites globally — and the crowds on peak days reduce the experience to something closer to a theme park than a heritage site. Weekday visits, particularly on Tuesday through Thursday, are significantly more manageable.
The best time of year is late October through December, when the summer visitors are gone, the weather is mild, and the light on the colonial buildings is excellent. Spring (March–April) is also good: the vegetation on the hillsides is at its greenest and the light is soft. Summer is hot, humid, and extremely busy. Winter is occasionally foggy, which has its own atmosphere. Arriving on the first morning ferry and staying until mid-afternoon gives the best balance of good light and manageable crowds on any day.