When will isa brown chickens start to lay

I got some isa brown chicks at the end of August. From what I have read, they will start laying usually between 20 and 22 weeks old. I have also read that they typically lay year round. My other chickens pretty much quit laying for most of the winter. My question is whether anyone else had fall isa brown's that came of age in the middle of winter. Will they start laying in the middle of January when they come of age? Or will they wait until the spring?

I don't have that breed, but while they might start laying in mid-January I'd expect them to probably not start laying, at least anything more than one here-one there, until light becomes more plentiful in the spring.  And if they go through a molt in the early spring it might be even later before you start getting significant production.

We've always gotten our chicks in the early spring (usually late March or early April), and they start laying around late JUly to mid August.  We have quite a variety, though we just lost our last French Black Copper Maran recently (the others were casualties of a coyote raid last winter).  She was just dead in the coop.  It appeared she was tucked in the night and was right by a water pipe.  We suspect she got frightened and accidentally broke her own neck (broken neck was the cause of death).

While breeds have trends, each bird is unique.  I have birds starting to lay right now (December) at various ages.  I'm pleasantly surprised by that, because indeed I've had pullets go "hm...  nope...  just gonna wait til spring to start that routine".   And some of my pullets are laying quite young despite being of breeds that often take 8-12 months to lay.  On the other hand, I have a dadgum fayoumi hen that JUST started laying, and she's 9 months old!!!  They're supposed to be one of the fastest maturing chicken breeds.  I've been highly unimpressed with the fayoumis I got.  My rooster died of obesity (pretty sure his genetics were screwed up bad, no one else was even overweight).  Though he did hold true to the breed and start crowing at like 3 weeks old!  And my hen didn't start laying til just now.  So much for that experiment, lol.

Anyway.  There's no definitive answer to your question.  She'll lay when she feels like it, for however long she feels like laying!  It also depends on the severity of your winters, how much light you supplement with, what kind of nutrition they're getting, how comfortable or stressed they are, and many other factors.

my 6 i got last april are still laying now but have slowed to every other day. the others have almost stopped completely since they are molting. never could see the benefit of molting in the coldest part of the season. they are in a uninsulated cabin and we have started to get -0f temps. poor bastards only have half their feathers! i give them extra corn and hot water 2xs a day to help them out.