Cat with Serious Infection

I got a text from my neighbor saying that there was a cat in the bushes behind my house.  After checking it out, it is a juvenile calico cat.  The poor thing has a massive URI.  I can tell from the condition of its nose and eyes.  It has no interest in leaving its spot where it has nestled in the bush.  My dog was barking at it for an entire day and I'm sure that it is terrified.  My problem is this....I have two cats in my house already.  This thing is very obviously sick but it is also suppose to be extremely cold tonight.  We have called animal control, but since it's already well past 5, I don't think they will be back tonight.  What are my options?

Hello and welcome to TCS. How's the cat doing this morning? Any news from Animal Control? It could be a feral cat and unless you know your way around feral cats, you shouldn't try and trap the cat on your own. 

The cat was very likely ferral and very, very sick.  I was able to get it into a feral house for a brief space of time but it got scared and ran into the neighborhood.  I haven't seen it since.