just some friendly advice ...
if this is going to be for an incubator for baby chicks (or something else along those lines) I'd check with someone who breeds chickens for a living ... my family used to raise chickens for an egg-farm operation back when I was a boy ... I can remember that there was more to keeping them alive than just the right temperature ...
if I remember correctly, there was something about the way the heaters (basically incandescent light bulbs) were arranged in "zones" - so that the little chicks could move back and forth from warmer to hotter by themselves ... and (again from memory) I think that humidity was a concern too ...
now if you're working on a project just to learn about PLCs then you've come to the right place ... but if you're trying to raise little chicks - I'd recommend that you talk to a company that sells ready-built incubators before you dive in too deep ...
either way - good luck with your project ...