In 2026, September in Osaka is far from cold; in fact, it is consistently one of the most humid and warm months of the year. While the "peak" heat of August has technically passed, daytime temperatures typically hover between 28°C and 32°C (82°F to 90°F). Because Osaka is located in a coastal basin, the humidity remains extremely high, often making the "real feel" temperature significantly hotter than the mercury suggests. September is also the heart of the typhoon season in Japan. Visitors should expect frequent, heavy rainfall and the occasional tropical storm, which can lead to rapid shifts in temperature, though it rarely drops below 20°C even at night. For travelers visiting in 2026, lightweight, breathable clothing and a high-quality umbrella are far more essential than a jacket. It isn't until very late October or early November that Osaka begins to feel "crisp" or cool, so those looking for autumn chill will find September much more akin to a lingering, tropical summer.