In the East, China starts to cool down after the hot and humid summer, and September kicks off the second most popular travel season in the country. It's also an excellent month to explore Japan before the crowds start to flock in October. While there might be occasional tropical storms or typhoons along the coasts of Japan in September, these typically last only 2-3 days and usually don't affect urban areas much. So, September remains a wonderful time to discover Indonesia and Borneo.