Curved Norfolk Island Pines (Araucaria heterophylla) in Balboa Park, San Diego, CA.

Is that because of wind or is it natural ?

It's most likely due to the prevailing winds.

We have the windswept pines here too...but they are the Eastern White Pine. They grow in the thin acid sandy soils around the lakes. Sometimes there are huge specimens on tiny islands and you wonder how they could survive.
I think I've said before how much I love the shape and colour of the Norfolk Island pines...house plants up here. So beautiful. Hope you are having a nice Christmas holiday. Wishing you all the best in the New Year, Andy.

I bet those windswept pines are so beautiful! I always love the shape the winds make on trees.

Norfolk Island Pine is a conifer; however, not a true pine. It's in the Araucariaceae family, not the Pinaceae family. It's an ancient family like Cycadaceae [cycads] (which is a conifer, also) from the Jurassic and Cretaceous periods.

I hope you have a wonderful New Year, also. :>)

I had such a great Christmas, the weather has been very hot here and now the temps are predicted to stay well above normal for January. It's not good for our severe drought, though.