Look at our poor goldline hen - what a big moult she had. She must have been chilly as she moulted in late November!
Hens moult every year but the time that they do so can vary greatly on the breed and on the conditions. Hens will normally moult towards the end of August or in September but it's not uncommon for a hen to moult as late as November.
The normal trigger for hens moulting is that the number of the daylight hours are shortening.
While your hen is moulting, you can expect her to slow down or even stop laying eggs for a while as they have to put a lot of work into making all those new feathers. Apple Cider Vinegar is a good generic tonic and helps chickens during stressful times so it's great for when they're moulting.
If your chicken has had a heavy moult really late in the year and you're concerned that they will get cold, try giving them hot mash (mash or pellets mixed with hot water) and some corn before bedtime to give them a carbohydrate boost for the evening.