January & February: It’s cold. Snow is possible at any time, particularly deeper in the valley at higher elevations. And though snow may look nice, it can affect travel and limit access, especially due to icy roads. Several locations deeper in the valley are closed this entire time, including the Double Vine Bridges and most historic houses. We generally do not offer guided tours in January and February. If visiting at this time, do yourself a favor and be sure to stay at a hot-spring hotel (onsen)!

March: The first half of the month can still be rather cold and the daytime coolness can linger till the end of the month (but it’s usually welcomingly milder by the later half of March). Snow can still occur at any time, including in the second half of the month, but it’s not particularly likely. The leaves will not yet be on the trees, so the overall landscape may seem a bit grey, and though the cherry blossoms always appear later in the Iya Valley than elsewhere in Japan, they will usually start to bloom in the lower part of the valley during final week or few days of the month. We usually do not offer guided tours during the first half of March, and during the second half of the month we do offer guided tours but we can not visit some locations, including some historic houses and the Double Vine Bridges, due to the winter closures which continue until April 1st. Due to accumulated snow at higher elevations, mountain hiking in March is not possible.

April: The days start to get more mild and warmer as the month progresses, but evenings will still be a bit cool. Most areas in the valley will have blooming cherry blossoms during the first week or two of April, but these lovely pink flowers can usually be seen up to nearly the end of the month at spots deeper in the valley. After the cherry blossoms fall, the leaves on the trees start to appear, and from the middle of April the forests start to look rather fresh and bright with their new leaves forming. All locations which were closed for the winter will now be open, except for mountain hiking, which only resumes in the last half of the month. It is not possible to go hiking in the first couple weeks of April, and even in the last couple weeks the trails can still have lingering snow on them, so it is not really recommended since there will also be no leaves on the trees yet at higher elevations. The sun sets in April at about 6:30pm and it is fully dark by about 7pm. And the final few days of the month begins the Golden Week holiday period, so this time can be quite busy. 

May: The weather is pleasantly warm (but not yet hot), maybe still a bit cool in the evening, and the trees have all developed their leaves, so the forests look bright and pretty. The days get increasingly longer, with the sun setting at about 7pm and getting fully dark at about 7:30pm. But even though May often has some of year’s the best weather, rain can still occur on any day (and can occasionally even happen for two or three days in a row). The first week of the month is Golden Week, which is always busy with visitors, and due to the pleasant weather, the final 3 weeks of the month are becoming an increasingly popular time to visit.

June: The weather is now consistently warm and can even feel a little hot around mid-day, but it is usually not so humid, so it usually feels rather pleasant. The beginning of the month usually offers fine weather (though rain can of course happen at any time), but by the second half of June begins the so-called rainy season. Though the skies can very often be overcast throughout this rainy period, it doesn’t necessarily mean constant rain all day on every day, and there is usually partial or even full days within this time when there is no rain and even some sun. And the exact starting time of the rainy season changes from year to year, and can start as early as near the beginning of the month, or as late as the final week of June. Also, the rains tend to creat beautiful fog formations that float through the valley and create a dreamy landscape. And though rather unlikely, the chance of a typhoon starts in June (in 2024 one even came on May 30th), along with the increased chance of linear rain storms. Please see about typhoons and linear storms down below. The sun sets in June at about 7:15pm and is fully dark about 30 minutes later.

July: For well into the first half of the month the rainy season usually continues (see June for info about the rainy times), but it’s often a bit undefined when it is fully finished, so there can commonly be a day or two of clear weather inter-mixed with days of rain. Linear rain storms can more often occur in July (though they are still rather rare), and typhoons have a higher chance of happening as the month progresses as well, but are generally not so common. (See about typhoons and linear storms below). By mid-July, as the rains end, it does get increasingly hot and humid during the daytime, but due to the higher elevation, mountain breezes, and dense forests, it is certainly not as unbearably sultry as elsewhere in Japan. The sun sets in July at about 7:15pm and full darkness is at about 7:45, and the evening temperatures in particular can be rather comfortable.

August: The days are often sunny and hot, but usually not nearly as uncomfortable as everywhere in Japan due to Iya being at a higher elevation and enclosed within the mountains. You’ll be happy to have escaped to the less humid Iya Valley area for sure after coming in from pretty much anywhere else in the country! But in mid-day it can still feel quite hot, especially if exerting oneself with hiking. Occasional rainy days are possible, and late afternoon thunderstorms can also sometimes happen. The chance of a typhoon has now increased to around its peak, especially from the middle of the month onwards, but it does not mean one is certain to happen (see about typhoons below). The Obon holiday period occurs for about a week from around Aug 10th to the 17th, so it can be quite busy during this time. The sun sets in early August about 7pm with full darkness at about 7:30pm, but sunset will be near 6:30pm by the end of the month and fully dark the at about 7pm.

September: The summer heat usually continues into the first half of the month, and it can still be rather warm till the end, but as the month progresses the humidity pleasantly recedes. and the approaching autumn air is often clear and refreshing. Rain can happen on any day here and there, but for the most of month the chance of typhoons is near its peak. It of course does not mean that a typhoon is going to happen for sure, and some years there has even been no typhoons in September (while other years they have happened multiple times). Please see about typhoons below. Expect the sun to set around 6:30pm early in September with full darkness at about 7pm, and sunset is a bit before 6pm by later in the month with it getting fully dark then a little before 6:30pm.

October: The weather is usually quite comfortable with occasional rainy days, and there is continuously less chance of a typhoon as the month progresses (but they can certainly still happen at any time in October). The autumn leaves at the higher elevations up on the mountain tops start to change color by about the middle of the month, with peak color usually happening up there in the 3rd or 4th week, so the last half of October can be a particularly nice time for hiking. Autumn leaves will start changing in the deepest parts of the valley (that are not up on the mountains) in the final week of the month. The days in October also begin to get noticeably shorter and a bit cooler in the evening, with it being fully dark outside well before 6:30pm at the start of the month, and by the end of the month it gets dark closer to 5:30pm.

November: The autumn leaves will be progressively changing color throughout the entire month based on the elevation (with deeper valley areas starting first, and lower areas happening more at mid-month), so for the first 3 weeks or so the forests will be at peak color at a one place or another within the valley, and the autumn colors even linger in some lower places right up to the final days of November. Along with the crisp and pleasant weather, and low-to-zero chance of a typhoon, November is accordingly one of the nicest times of the year to visit. The daytime temperatures are usually mild, with evenings becoming increasingly chilly, and by the last half of the month the mountain tops will potentially start having snow. The final half of the month can even feel a little bit cold out deeper in the valley. A rainy day or two can occur at any time, and the sun sets at about 5pm, with it being completely dark outside by 5:30pm. Though hiking is still possible for most of November, we really do not recommend going hiking after the first week or so of the month. At the higher elevations on the mountains the autumn leaves will have already completely fallen by the start of November, and as the month progresses it gets increasingly colder up on the mountains, with the summit winds often making it feel a bit frigid even at mid-day by the middle of the month. 

December: The weather gets increasingly colder and snow becomes more possible as the month continues. The autumn leaves will be finished. From December 1st several places deeper in the valley close for the winter, including some historic houses and the Double Vine Bridge. Guided tours are still usually possible for the first half of the month, but we usually do not offer guided tours in winter starting from mid-December. 

Rain, Typhoons, and Linear Storms

While most of Japan tends to have a “rainy season” from about mid-June to mid-July (plus or minus a week or two on either end), there is not really a specific dry season, so rain can occur at any time. Throughout the year, sometimes it can rain for several days in a row, while other times it may be dry for a week or two or more. However, a rainy day usually creates beautiful drifting fog formations in the Iya Valley which are uniquely beautiful to see, and we also have umbrellas available for everyone to use when walking on the tour. But we generally do not recommend trying to go mountain hiking in the rain because the mountain tops can be covered with clouds and offer no views. When arranging to go hiking, we always try to have a secondary tour plan in case hiking is not possible that day.

Typhoons are large storms that can happen at anytime from June to November, with peak chance of occurring probably from mid August till late September. In Shikoku, typhoons are simply a fact of life, and due to their far-reaching expanse of creating wind and/or rain, usually the Iya Valley area is affected by at least 5 or 6 of these large storms per year (but some years it can be as little as 1 or 2, and other years it can be 10 or more). The most intense affects of the storm can last in the area from about 12 hours up to 2 days, and the amount of rain released can be quite incredible (and they can also include linear rain-bands, see below). Usually typhoons are forecast at least 3 or 4 days before they are to hit the area, so we can usually make counter plans with any tour that may be affected, however it may mean just needing to cancel things. Also, local roads and most sights often close if the weather is severe, and the train lines to/from Oboke Station often also close. If you are scheduled to have a tour during a predicted typhoon, we will be in contact with you beforehand to plan accordingly, but please understand that we may be limited with what we can do.

And though it is not necessarily part of either a typhoon or the rainy season, from mid/late spring until late summer anywhere in Japan can experience a linear rain-band storm. These difficult to predict phenomenon are when a localized area (maybe 20 to 50km wide and 100 to 300km long, though sometimes bigger) gets intense heavy rain for anywhere from 3 or 4 hours up to 2 or 3 continuous days in a row, while a neighboring area just 40 or 50km away may be completely clear and sunny during the same time. Though linear rain-bands can happen as part of a typhoon, they can also happen independently, yet such independent cases are a bit more rare (maybe just 10-15 times per year throughout southern Japan, but sometimes more). If one occurs in or near the Iya Valley area separate from a typhoon, then roads within, around, or leading into the area may become closed, and/or the trains going to/from Oboke Station (or elsewhere) may also be suspended, so this could affect your travel plans into the area and/or our tour in general. If this is the case, we will be in contact with you to adjust things as necessary.