Climatology of Tokyo

Tokyo lies in the humid subtropical zone or can be classified by the Koppen-Geiger scheme as Cfa.  This means Tokyo has generally, hot humid summers and mild winters with cool spells.    

Some meso-scale climate controls that affect Tokyo are location and a major ocean current.  Because Japan is an island it's climate is deeply affected by its location on the Pacific Ocean and the Sea of Japan.  The tropical weather from these bodies of water bring substantial amounts of rain into Tokyo.  Generally, the marked rainy season is early June, lasting about a month.  On average, five or six typhoons pass through Tokyo from early August to early September.  In the winter, a high pressure area develops over Siberia and a low pressure area can develop in the Pacific Ocean bring cold fronts into Tokyo resulting in lower, colder temperatures. Snowfall is sporadic, but does occur almost annually.  

The major ocean current that affects Tokyo is the Kuroshio current, also know has Black Current, which is also known as Japan current.  This warm water current flows northward on the Pacific side of Japan which warms Tokyo and surrounding areas of Japan.  

A micro-scale climate control of Tokyo is the urban heat island effect. According to the Tokyo Metropolitian Government,  the annual mean temperature has increased about 5.4 degrees F over the past 100 years.  The city has been cited as a "convincing example of the relationship between urban growth and climate." This can be attributed to Japan's fast growth rates in the late 19th and early 20th centuries.  Today, Japan is home to roughly 127 million people.  

This image shows the Kuroshino ocean current that affects Tokyo's climate.

blog.geogarage.com

This is a climate graph of Tokyo for the averages throughout the year. 

http://www.climatetemp.info/japan/tokyo.html

This is a weather graph of my weather station in November 2003.

This is a weather graph of my weather station in November 2011. 

When comparing November 2003 to November 2011 low temperatures, it appears the the lower temperatures are higher than they were eight years ago.  There is also less daily rainfall annually than in 2003, this could also be a very dry year for Tokyo and doesn't summarize the total changes in Tokyo's weather patterns.