Weather for Dec 2018

My visit to Kyoto from 14th to 18th Dec 2018 and Osaka from 18th-26th 2018

How would the temperature be like, Should I need a windbreaker at Kyoto and Osaka ?

Thank you.

Regards,
Karen

Yes; it sounds better to prepare a winter jacket or a half coat.
In Kyoto City you might see the first snowfall of the season.

[From 14 to 26 December in the years from 2013 to 2017]  

-- Kyoto --
The lowest temperature in a day
: -1.7 to 9.6 degrees C.
The highest temperature in a day
: 3.5 to 18.3 degrees C.
The difference in the temperature in a day
: 2.4 to 11.4 degrees.

-- Osaka --
The lowest temperature in a day
: 0.2 to 11.3 degrees C.
The highest temperature in a day
: 4.7 to 21.2 degrees C.
The difference in the temperature in a day
: 2.6 to 10.2 degrees.

[December in the 30 years from 1981 to 2010]

-- Kyoto --
The average of the lowest temperature in a day
: 3.2 degrees C.
The average of the highest temperature in a day
: 11.6 degrees C.

-- Osaka --
The average of the lowest temperature in a day
: 5.1 degrees C.
The average of the highest temperature in a day
: 12.3 degrees C.