Pogoda Nikkō — sierpień

August is widely called Japan's worst month - wet, sticky heat with nights that stay above 30C - and Karuizawa exists as the answer to it. Our row gives 25.7C by day and 17C at night, which is the gap that made this a resort town and filled it with Tokyo second homes; it is an hour by shinkansen. What the escape costs is rain: 194.9mm across 22.2 precipitation days at 85 percent humidity, as wet as June even with the tsuyu long finished. The crowd date is Obon, around the 15th, when Karuizawa gets properly busy - though regulars note it is nothing like New Year or Golden Week. The record: feels-like 29C, 9.8 hours of sun, a 7.8 kph wind and AQI 46.

Regulars are specific the lower Toshogu area can turn cold and rainy with sleet even as the mountains above stay genuinely hard to predict, snow at higher elevations a real possibility - one memorable year even brought a snowstorm as late as April 1st. Our row backs that cold, genuinely wet read, 10.1C over -0.1C nights feeling as low as -4C, with a substantial 131.9mm of rain across 14.6 days and real snow, 32.4cm. Regulars are consistent Lake Chuzenji specifically runs colder and more exposed than the lower town, staying cold and crisp even late in the month. Thick coats, hats and gloves remain the standard advice throughout rather than an early-spring wardrobe. The record: humidity 73 percent, 8.5 hours of sun and a 13 kph wind.

September here can be too foggy and wet for good visibility, and regulars say October and November both run drier - our row backs that with 241.5mm across 23 days at 87.9 percent humidity, easily this destination's wettest column of the ones we carry. The consolation is Kegon Falls itself: the volume of water is at its best now, and visitors who caught a clear late-September day call the falls robust and colourful with the season's first hints of colour already showing. Peak foliage in the upper park is a month or more away, mid to late October. Our temperature reads gently, 23.8C over 17.6C, with only 7.5 hours of sun a day standing behind that rain total. The record: an 8.4 kph wind and AQI 38.

The colour here is a question of altitude, not date. Regulars are blunt that the town and shrine area is mostly cedar and does not turn at all, so the autumn everyone comes for is up the Irohazaka road at Chuzenji and Kegon, and by late October that upper ground is in full colour. The cost is the same road: weekends are extremely crowded and the bus up to Oku Nikko can hold you for hours, so the advice is a weekday and a very early start. Light layers do it in October at 17.9C over 10.6C. Our row adds what the board leaves out - 197.7mm across 17.4 days and only 7 hours of sun - so this is a wet month to be planning a view in. The record: humidity 84 percent, a 9.2 kph wind and AQI 32.

For once our snow column is not describing a distant hillside: visitors to Nikko in early April report actual snow, very cold air around Kegon Falls, and at least one April storm that made roads impassable, which is what the 8.5cm in our row is. The split to plan around is inside the destination. Downtown Nikko is the mild part at 15.2C over 4.8C; up at Lake Chuzenji, several hundred metres higher, the mountains are still white and the woods still under snow while the town below is in spring. If the Fukiware-to-Chuzenji road closes there is a low route that adds about two hours. And regulars are blunt that this is not a cherry-blossom destination - Nikko is deciduous forest, not sakura. The record: 142.6mm across 14.9 days, 9.1 hours of sun and AQI 55.