The greater Tokyo area will be seeing partly cloudy skies for much of the week. Daytime temperatures will be cool, mainly in the low-mid 20s°C (70s°F). Evening lows will be warm, in the upper-teens °C (60s°F).

What clothes to pack for Tokyo in May?
・Pack layers: Light warm clothes for early spring that you can remove during the day as temperatures rise.
・Short-sleeved shirts; jeans or light slacks; comfortable sneakers or walking shoes are recommended.

Japan nationwide
Looking at the weather forecast for the rest of Japan, most areas will be seeing overcast skies and warm temperatures from the beginning of the week.

Northern Japan
Hokkaido and the north country are expected to see cloudy skies this week. Daytime highs will be around in the mid-upper teens. Evening temperatures will be in the upper single digits.

Central Japan
The greater Osaka and Kyoto area is expected to see partly cloudy skies through the week, with rain Monday and Tuesday. Temperatures will be hot, with highs in the upper 20s °C and lows in the mid-teens °C.

Okinawa
As for Okinawa, expect partly cloudy skies and rain throughout much of the week in Naha. Daily highs are expected to be in the mid-upper 20s℃, with lows in the mid-20s.

No tropical storms are currently in the forecast for Japan.

Details on storms can be found on the Japan Meteorological Agency website.

Check the links below for more on upcoming fun events and festivals!

・Latest Typhoons/Tropical Cyclone Information: http://www.jma.go.jp/en/typh/
・Latest Earthquake Information: http://www.jma.go.jp/en/quake/

Source for forecast and images: Japan Meteorological Agency website / http://www.jma.go.jp/jma/indexe.html