Weather question and what to wear

My visit to Osaka from November 13th-24th, from a bit of searching, last year it was approximate 16c-18c, how would the temperature be like, would wearing T-shirt and shorts be alright, or would I need a Jacket or windbreaker.

It depends on you. I would be fine in a t-shirt in 16-18C, but other people will be rugged up with jackets. Also, while the daytime high might be 18C, nights and daily variation would see temperatures probably range from low teens to low twenties. Take something warm.
Last November I had days with great sun and nice temperatures around Kyoto and down to Hiroshima, and I also hit heavy snow in the mountains/Takayama. The snow required more than just a t-shirt, it was about 6C in the middle of the day.

That depends on how tolerant you are to cold. I have a friend from Pittsburgh that claims to wears T-shirts only all year, even in Pittsburgh.

You got the temperature data, but don't forget to consider the wind chill factor, also. Those winds can pierce through between buttons, so I wear a jacket with double-breast type zipper closure.

from a bit of searching, last year it was approximate 16c-18c

Your source may be incorrect or unreliable.

According to the database of JMA,
at Osaka observatory site
during those 12 days in November 2017,
the temperature
was 4.8 degrees C at lowest and 18.6 degrees C at highest,
and the highest temperature of a day
was 10.2 degrees C at lowest.

In November,
the gap between the highest and lowest temperature of a day
may reach around 12 degrees.

(This observatory site is on Osaka Plain and near Osaka Bay.
Temperature may be lower on highlands.)

It sounds better to prepare for chilly air,
especially you would be outdoors in the evening or early morning,
though of course it may depend on persons.

Enjoy your trips!

Thanks for the information, I am able to withstand the cold temperature when I used to live in the UK, but since I now live in Hong Kong, I have become used to warmer temperature, but if its not too cold, I'm alright with that, so probably knee high shorts and T shirt should be ok, I will also carry a windbreaker. I have experienced 5 degree C in Japan in December driving between Tokyo and Fukushima, and experienced even colder temperature in the same period in Tokyo Asakusa in the middle of the midnight searching for a hotel when my flight was delayed.

We usually get to Nara on around the 25th November, by that stage it is very, very icy (for us who live on the Gold Coast). Mornings would be under 8 degrees, it is generally nice in the sun but very cold in the shade. Once the winds pick up it is a lot colder.

I tend to wear one really heavy jacket over a tee shirt, which suits Japan in my experience as it is always so hot inside shops/restaurants/transport, and with one heavy jacket you take it off and are fine, rather than ending up with a pile of clothes sitting next to you.

This year we will be there late October/early to mid November but I think I will still just do the one jacket thing. You can unzip it if it is too warm.

Thanks for the reply, I only have two Jackets, and those are down to the knee type, so that out of the question, one of them are those three in one type, may be I could just wear the inner part which is a thin fleece part, or I will just buy a double layer wind breaker.
I'm alright with the whether in Tokyo, just wasn't sure what it's like in Osaka/Nara/Kobe/Kyoto and Amanohashidate a few places I will be visiting this November, just hope it doesn't rain especially on the 18th whiles visiting Amanohashidate.