Osaka is a year-round destination but has distinct seasonal high points. Spring (late March to early May) brings cherry blossom — Osaka Castle Park and the Mint promenade are the best spots — and comfortable temperatures around 12–18°C. This is the busiest period; book accommodation well ahead.
Summer (June to September) is hot and humid, with temperatures regularly above 35°C and a rainy season in June and July. The Tenjin Matsuri on 24–25 July is the highlight of summer — one of Japan's three great festivals, with a river procession of illuminated boats and fireworks over the Okawa River. The heat makes sightseeing exhausting; the city shifts to a nocturnal rhythm after dark.
Autumn (October to November) is the best season for walking: temperatures of 15–22°C, clear skies, and autumn foliage in Minoh Park. Winter is cold but mild by Japanese standards — rarely below freezing in the city — and crowds are thinner from January to February.