1 Overnight temperatures are generally warm with an average low of 20.2 °C (68.4 °F). 2  In September the range/ variation of daily average temperatures is 6.5 °C (11.7 °F).  The weather in September is very slightly soggy with occasional rain. Around 179.8mm (7.1in) of H2O accrues across an average of 13 days.
http://www.tokyo.climatemps.com/september.php
Here is a summary of seasonal weather: http://www.japan-guide.com/e/e2273.html It seems to me that rain is unavoidable unless you travel in the dead of winter. I don't even pack rain gear--I just buy a cheap umbrella at the nearest convenience store when the rain starts. I've been in Tokyo twice during typhoons.
https://www.tripadvisor.com/ShowTopic-g298184-i861-k6060622-Silly_to_visit_Tokyo_in_September-Tokyo_Tokyo_Prefecture_Kanto.html
The following weather averages for Japanese cities are representative of the major regions of Japan: September is the rainiest month of the year in Tokyo. Tokyo is generally a rainy city with annual rainfall of 1528 mm that makes other rainy cities such as Vancouver (1153 mm) and London (601 mm) look dry. Tokyoites are accustomed to the rain and it doesn't slow down the pace of life. A reasonably good umbrella can be purchased in Tokyo for 1000 yen or less.
http://www.japan-talk.com/jt/new/september-weather-in-japan
1 The average temperature in Tokyo in September is fairly hot at 23.2 °C (73.76 °F).  Afternoons can be hot with average high temperatures reaching 26.7 °C (80.1 °F).
http://www.tokyo.climatemps.com/september.php
September is hot, rainy and dark throughout much of Japan due to the effects of the typhoon season that peaks in August and September. Typhoons tend to affect the weather, even when they don't directly strike Japan.
http://www.japan-talk.com/jt/new/september-weather-in-japan
1 The average temperature in Tokyo in September is fairly hot at 23.2 °C (73.76 °F). 2  Afternoons can be hot with average high temperatures reaching 26.7 °C (80.1 °F).  Overnight temperatures are generally warm with an average low of 20.2 °C (68.4 °F).
http://www.tokyo.climatemps.com/september.php
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https://www.wunderground.com/jp/tokyo
1 The weather in September is very slightly soggy with occasional rain. Around 179.8mm (7.1in) of H2O accrues across an average of 13 days.  The heavens above Tokyo are a little dull with an average of a modest 4:23 of glaring solar radiation daily.
http://www.tokyo.climatemps.com/september.php
1 The average temperature in Tokyo in September is fairly hot at 23.2 °C (73.76 °F). 2  Afternoons can be hot with average high temperatures reaching 26.7 °C (80.1 °F). 3  Overnight temperatures are generally warm with an average low of 20.2 °C (68.4 °F).  In September the range/ variation of daily average temperatures is 6.5 °C (11.7 °F).
http://www.tokyo.climatemps.com/september.php
Hi all, We are planning our first trip to Tokyo for September 2014 and will be arriving in the last 2 weeks of September for 10 nights. I have read that September can be typhoon/rainy season for Tokyo and am wondering if we are silly to consider visiting at this time.
https://www.tripadvisor.com/ShowTopic-g298184-i861-k6060622-Silly_to_visit_Tokyo_in_September-Tokyo_Tokyo_Prefecture_Kanto.html
weather in tokyo japan in september
In Tokyo, Japan, the weather is fairly hot at 23.2 °C in September. In September, the temperature of Tokyo, Japan is fairly hot at 23.2 Degrees Celsius.