A hot tub is maintained at a constant temperature irrespective of the external temperature so that it is always ready and always pleasantly warm. You may need to wear a robe to walk from the centrally heated holiday cottage in the winter to the hot tub sited in the garden and you will definitely be pleased to submerge yourself up to your shoulders once you get there.
Admittedly, a dip in the hot tub during cold weather is a bit of a bracing experience. It could be the kind of thing that a group of friends might try for fun during a winter break. If the temperature of the water is high enough compared to the environment, you will probably sit in a cloud of steam
It is not the same as the gentle and relaxing pamper session in the summer.