Hi Alex,
I was in Langebaan end of December. Temperature, Wind etc. were perfect. My Page is a review Page so it’s about the time I was there and I can’t answer your question unfortunately in that details. I suggest you ask at the local kiteschools e.g. http://www.kitesurfinglangebaan.com I am sure they can answer you Qestions in Detail. Hope this works for you!
Best,
Mathias