Iwakuni, in Yamaguchi Prefecture, enjoys a humid subtropical climate with four distinct seasons. Summers are hot, humid, and rainy, while winters are cool, mostly dry, and often clear. The city experiences moderate annual rainfall, mild temperature swings, and is known for its cherry blossoms in spring and colorful foliage in autumn.
The best times to travel section shows how the months compare for a visit, so you can find the time of year that fits what you want to do.
Background colors of the months:
The color shows the typical temperature: yellow (hot), green (mild) and blue (cold). How strong the color is shows the travel season: full color means high season, soft color means shoulder season and soft-striped means off season.
Weather symbols:
Each month has one symbol showing what the weather is typically like, such as hot and sunny, freezing or a rainy or snowy season. Use them to quickly spot months that match the weather you want, or to avoid the ones that don't.
Crowdedness:
The people icon shows how busy the place usually is. The more people, the more crowded it gets.
Additional notes:
The gray info boxes point out special things worth knowing, like recurring weather issues or seasonal events.
Iwakuni’s climate features notable seasonal variation, shaped by its coastal location near the Seto Inland Sea. Average annual temperatures hover around 16.5°C. Summers (June–August) are hot and humid, with average highs reaching 31–32°C in August and lows near 23–24°C. The rainy season, or tsuyu, typically runs from early June to mid-July, bringing heavy precipitation – June and July each receive around 280–300 mm of rain. Typhoons can occasionally affect the area from late summer to early autumn, but the city is somewhat sheltered by surrounding mountains and the inland sea.
Winters (December–February) are cool and mostly dry, with average highs of 8–11°C and lows around 2–4°C. Snowfall is rare in the city but possible in the nearby mountains. Spring (March–May) and autumn (September–November) are especially pleasant, with mild temperatures (14–24°C), lower humidity, and abundant sunshine. These seasons are ideal for outdoor activities, cherry blossom viewing in April, and enjoying autumn foliage in November. Iwakuni receives about 1,600 mm of rainfall annually, with the wettest months being June and July, and the driest in winter. Sunshine is plentiful, particularly in spring and autumn, with daylight ranging from about 10 hours in winter to over 14 hours in summer. Winds are generally light, though can be brisk in winter or during storms.
The city’s climate supports lush greenery in summer, vibrant seasonal flowers, and comfortable conditions for sightseeing and outdoor experiences most of the year.
| Average climate data for Iwakuni, Japan | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Average maximum temperature (°F) | 46 | 47 | 54 | 61 | 70 | 74 | 81 | 85 | 78 | 69 | 60 | 49 | 85 |
| Average minimum temperature (°F) | 37 | 38 | 42 | 49 | 57 | 64 | 72 | 74 | 68 | 59 | 50 | 41 | 37 |
| Average precipitation (inch) | 1 | 1 | 2 | 2 | 2 | 3 | 5 | 3 | 2 | 2 | 1 | 2 | 26 |
| Average rainfall days (days) | 13 | 12 | 12 | 12 | 11 | 16 | 20 | 17 | 14 | 10 | 10 | 14 | 161 |
| Average snowfall (inch) | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Average snowfall days (days) | 5 | 3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 10 |
| Average relative humidity (%) | 74 | 73 | 73 | 74 | 76 | 82 | 86 | 82 | 80 | 77 | 76 | 77 | 77 |
| Average wind speed (mph) | 7 | 7 | 6 | 6 | 5 | 4 | 5 | 5 | 5 | 6 | 6 | 7 | 6 |
| Average daily daylight hours (h) | 10 | 11 | 12 | 13 | 13 | 14 | 14 | 13 | 12 | 11 | 10 | 9 | 12 |
| Average daily sunshine hours (h) | 5 | 5 | 7 | 9 | 9 | 8 | 9 | 10 | 9 | 6 | 6 | 5 | 7 |
| Average cloud coverage (%) | 43 | 41 | 39 | 36 | 32 | 43 | 41 | 32 | 35 | 32 | 33 | 42 | 37 |
| Average UV index | 2 | 3 | 3 | 4 | 5 | 5 | 7 | 6 | 5 | 4 | 4 | 2 | 4 |
The best times to visit Iwakuni are in spring (April to May) and autumn (October to November). These months offer mild temperatures, low humidity, and abundant sunshine, making them perfect for sightseeing, enjoying cherry blossoms or autumn foliage, and outdoor activities. Rainfall is moderate and weather conditions are generally stable.
The least favorable time to visit Iwakuni is during the rainy season in June and July, when humidity and rainfall are at their highest. Summer (July–August) can also be uncomfortably hot and humid, with occasional typhoons disrupting travel plans. Winter, while mild, is less attractive for those seeking warm-weather activities.
Iwakuni’s average annual temperature is about 16.5°C. The coldest month is January (average high 8°C, low 2°C), while August is the hottest (average high 31–32°C, low 23–24°C).
Iwakuni receives around 1,600 mm of rain annually. The wettest months are June and July, with heavy rainfall during the rainy season. Winter months are much drier.
Snow is rare in Iwakuni city. Winters are generally cool and dry, but the nearby mountains may see occasional snowfall, especially in January and February.
Cherry blossoms typically bloom from late March to early April in Iwakuni. This is a popular time for visitors, with many parks and riverside areas hosting hanami (blossom viewing) events.
Typhoons can occasionally impact Iwakuni, especially from August to September. While direct hits are rare, travelers should monitor weather forecasts during this period for potential disruptions.
Pack light layers for spring and autumn, breathable clothing and rain gear for summer, and a warm jacket for winter. An umbrella is essential if visiting during the rainy season.
Iwakuni enjoys abundant sunshine, especially in spring and autumn, with 5–9 hours of sunshine per day. Winter months are cloudier but still have bright days.
The warmest month, with the highest average maximum temperature, is August (84.6 °F). The month with the lowest average maximum temperature is January (45.6 °F). Overall, the average maximum temperature over the whole year is 64.5 °F.
The month with the highest average minimum temperature is August (73.9 °F). The coldest month, with the lowest average minimum temperature, is January (37.2 °F). Overall, the average minimum temperature over the whole year is 54.1 °F.
The wettest month, with the highest amount of precipitation, is July (5.4 inch). The driest month, with the least amount of precipitation, is November (0.9 inch). Over the whole year there are 25.7 inch of rainfall on average.
The month with the most days of rain is July (20 days). The month with the fewest days of rain is October (9.7 days). Over the whole year there are 160.9 days of rain on average.
The month with the most snowfall is January (0.5 inch). The months with the least snowfall are April, May, June, July, August, September, October and November (0 inch). Over the whole year there are 1.1 inch of snowfall on average.
The month with the most days of snowfall is January (4.8 days). The months with the fewest days of snowfall are April, June, July, August and November (0 days). Over the whole year there are 10.4 days of snowfall on average.
The month with the highest average relative humidity is July (85.7 %). The month with the lowest average relative humidity is February (72.9 %). The overall average relative humidity over the whole year is 77.5 %.
The windiest month, with the highest average wind speed, is January (7.4 mph). The calmest month, with the lowest average wind speed, is June (4.2 mph). The overall average wind speed over the whole year is 5.7 mph.
The month with the cloudiest skies, so the highest cloud coverage, is January (42.5 %). The month with the clearest skies, so the lowest cloud coverage, is October (31.6 %). Over the whole year there is an average cloud coverage of 37.3 %.
The month with the longest days, so the most daylight, is June (Average daylight: 14 h). The month with the shortest days, so the least daylight, is December (Average daylight: 9.1 h). Over the whole year there are 11.9 h of daylight per day on average.
The month with the most sunshine per day is August (Average sunshine: 10 h). The month with the least sunshine per day is December (Average sunshine: 5 h). Over the whole year there are 7.4 h of sunlight per day on average.
The month with the highest average UV index is July (UV index: 7). The months with the lowest average UV index are January and December (UV index: 2). Over the whole year the average UV index is 4.2.
