Weather in September

Hello,
Where can I find relaiable local site with estimated weather on September in various places in Japan?
Looking for recommended tips as in need coat and gloves or just long sleeves...
Especially in Koyasan and Takayama

This website has a weather section.

Also many on a simple google search. Then just check temps from prevoius years.

Koyasan and Takayama are a mountain area/higher elevation so you might need a light jacket for the evening/night time. But during the day its humid still in September. Places outside of the mountain higher elevation area are still warm enough not to wear a coat even at night up to November or December.

As a british person I couldnt believe hot it was in Japan in late September. Koyasan daytime temperatures will be in the low to mid 20's C https://en.visitwakayama.jp/plan-your-trip/wakayama-climates/ Takayama will be similar https://weather-and-climate.com/average-monthly-Rainfall-Temperature-S...

@Stan its because Japan is mostly in line with California and Baja California and is humid like places such as Florida and Georgia, its considered subtropical, so winters are short, summer is long. September is still part of the summer weather in Japan. That is why you will see palm trees randomly growing all over Japan (Honshu, Shikoku and Kyushu) even in mountain villages you will see random palm trees. Banana plants can be seen sometimes by people's houses too. And it's why Japan can grow citrus like sudachi and oranges and olives too. Also why there are typhoons which are basically tropical storms.