Japan Rugby World Cup Monthly Rainfall and Temperature Outlook

Updated: 12 September 2019

The Rugby World Cup is set to start with the Japan versus Russia clash on Friday the 20th of September at Tokyo Stadium.

There has been a lot of discussion in the media about what the weather might be like and how it could influence the tournament. With venues stretched across the island nation from the Sapporo Dome in Hokkaido in the north to Kumamoto Stadium in Kyushu in the south we are looking at nearly 1500 kilometres (or close to 900 miles) of diverse geography in between. Over the life of the tournament we can expect a range of weather conditions.

Four of the venues have either a permanent roof such as the Sapporo Dome or retractable roofs: City of Tokyo Stadium, Kobe Misaki Stadium or Oita Stadium. That leaves the remaining eight venues and the teams and fans exposed to the elements in the case of inclement weather.

Planning for the weather is something all teams and fans do. Regular weather forecasts for game day are available from multiple sources. The team at CLIMsystems and ExtendWeather fill an important gap by providing month by month outlooks so that longer term planning can be considered.

The RWC is being played during typhoon season. Predicting the risk of a typhoon months in advance is not possible but foreseeing how much warmer/colder or wetter/drier than normal conditions may prevail is possible.

We have already seen teams adjust their training schedules owing to warmer than normal conditions this September. How might those conditions change in October and November? That is why we will be generating outlooks that we will update approximately every ten days during the RWC.

September through November Rainfall Outlook Percentage Change from Historical (outlook released 2 September 2019)

Rainfall Synopsis

Historical September rainfall across all the venue ranges from 142 mm in Kumagaya Rugby Stadium to the northwest of Tokyo to a high of 259 mm at Shizuoka Stadium Ecopa located in Fukuroi City located about 240 km southwest of Tokyo. Most venues average around 200 to 250 mm for the month.

The outlook for September however is for wetter than normal conditions for most venues. Fukuoka Hakatanomori Stadium could be up to 14 percent wetter than normal. Most of the other venues could be between 8 and 10 percent wetter than normal. City of Toyota Stadium should be near normal while only the International Stadium and Shizuoka Stadium Ecopa could be drier than normal.

October and November rainfall on average decreases from the highs in September. However, the seasonal outlook for both months is for wetter than normal conditions in both months and for November considerably wetter than normal conditions for some areas. We will highlight specifics about October and the finals venue with subsequent seasonal outlooks.

September through November Temperature Outlook Degrees Celsius Change from Historical (outlook released 2 September 2019)

Temperature Synopsis

Historical September MEAN temperatures across all the venue ranges from 17.5 degrees C at the Sapporo Dome in Hokkaido to 24.0 degrees C for Ōita Stadium Ōita Prefecture on Kyushu Island located about 760 km southwest of Tokyo. For most venues MEAN average temperature is in low 20s Celsius for the month. Note that these are the average MEAN temperatures not the average high or low temperatures for the month.

The outlook for September is for the MEAN temperature to be warmer than normal for all venues. Only Oita Stadium is likely to be close to normal. With Kamaishi Recovery Memorial Stadium in Kamaishi City possibly averaging over 1.1 degrees C above average for the month. Most of the venues are in the 0.7 to 1.0 degree C above average range. In general, the month of September is as we have already been hearing likely to be warmer than normal.

As expected, October and November monthly average temperatures decrease slowly, however the longer-range outlook is for both months to be warmer than normal. The outlooks for these months will be highlighted in subsequent seasonal forecasts.