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Hiroshima sits on the delta of the Ota River on the southern coast of Honshu, facing the sheltered Seto Inland Sea in western Japan at approximately 34.39°N, 132.46°E. Its position on the Inland Sea gives it a mild humid subtropical climate (Köppen Cfa) — hot summers and mild winters — with more fine days and less rain than either the Pacific or Sea of Japan coasts.
Summer, from June to August, is hot and humid, with August the warmest month — average highs around 32–33°C and muggy nights. Early summer brings the baiu plum rains of June and July, which can be heavy enough to cause landslides on the steep slopes ringing the city, and late summer brings the risk of typhoons tracking up from the Pacific.
Winter, from December to February, is mild, with January the coolest month — average highs around 9–10°C and lows near 1–2°C. Frost is common on clear nights but snow is infrequent and rarely lies, since the mountains of Chugoku shield the city from the heavy snow that buries the Sea of Japan coast just to the north. Days are often clear and sunny.
Hiroshima receives around 1,500–1,600 mm of rain a year, concentrated in the baiu rains of June and July and again in the autumn typhoon season, while winter is dry and sunny; the sheltering mountains keep totals lower and fine days more frequent than on the exposed coasts. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.
The mountains of Chugoku and Shikoku block the seasonal winds from both sides, giving the Seto Inland Sea region — including Hiroshima — a mild climate with many fine days year-round. Its steep, granite hillsides, however, make it dangerously prone to landslides during the torrential baiu rains, as in the deadly debris flows of 2014 and 2018.
To follow any single measurement in Hiroshima more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.