When to go: September vs. October?

[mamut]

I didn’t find much information in the forum about traveling in the fall.

I plan on traveling for three weeks. Roughly the plan is to visit Tokyo and surroundings, Nagano and surroundings, Kyoto and surroundings and Hiroshima/Mijayima Island.

I had hoped to go in April but didn’t work out because of work. So now I am looking at anytime after August. From what I’ve read October is recommended. But before I decide I wanted to know the following:

Besides September being warmer, is there anything else that separates them? Are typhoons likely, rainy days/humid weather?

Should I expect fall colors in mid October? I don’t think I’ll stay past mid-October.

Are there festivals that might sway me to one or the other?

Just another tidbit I found that surprised me was the sunset times of at 6pm or earlier so early in the season.

Thank you.

[chachava]

Head out as late in October as you can for the changing colours...

Pretty sure it was still fairly humid through September so I don't recommend being here for that (it was horrible!)

As for typhoons, the biggest ones are usually September because of the changing conditions...