: how the weather is like..whether it is raining or dry? Weathers in Japan in that season depend on Autumnal Rain Front and typhoons. Where and when a typhoon stimulates Autumnal Rain Front unfortunately, most of peoples can not but stay indoors due to heavy rain.
I think you'd better book your hotel for consecutive nights so that you can stay in daytime (during the reservation period) in case you cancel your outdoor trip.
Of course it's not that all parts of Japan are rainy or stormy every day in September.
You will travel among the four places moving mainly in Pacific half of Honshuu mainland and Northern Kyuushuu, and you will have 16 days; so I don't deny chances of visiting some sites, free from Autumnal Rain and typhoon storms.
However, generally October is better for outdoor holidaymaking in Japan, with less risk of bad weathers. (It was about 45 years ago, but Tokyo Olympic Games started on October 10.)
Roughly speaking:
- Autumnal Rain falls mainly on Northern Japan and Japan-Sea half of Honshuu mainland.
- Compared to summer typhoons, an autumn typhoon migrates faster, not so wonderingly, except when plural typhoons exist close.
By the way, September 19 through 27 of 2009 include a row of holidays in Japan.
Sept.19 = Saturday; Sep. 20 = Sunday; Sep. 21 through 23 = Holidays;
Sept.24 and 25 = Weekdays; Sept.26 = Saturday; Sep. 27 = Sunday.
I guess there will be people who take a mini vacation for these 9 days.
Maybe some attractions in famous tourism places will be crowded during this period.
Japan Meteorological Agency: English Top
http://www.jma.go.jp/jma/indexe.html
Japan Meteorological Agency: Weather Warnings/Advisories
http://www.jma.go.jp/en/warn/index.html
Japan Meteorological Agency: Typhoon Info
http://www.jma.go.jp/en/typh/
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