I am in social sciences, in 3rd year, in an honours program. I got a couple marks back already and I am guessing that my overall year average is going to be around a 5.

In social sciences, I need at least a 6 to continue in 4th year in my honours program.. if I take summer courses, can this add towards my CA and allow me to continue? I had a hard time this year and my marks definitely suffered.. but I am confident that I can bring it up. I know the other option would be to leave mcmaster and take the BA, but I would much prefer to stay for the 4th year and get the honours BA. Thanks for the help

You should see an advisor ASAP.

If you still lack the degree requirements to graduate with a BA, ie dropped courses and don't have enough to graduate, or if you are missing some pre-reqs, Then you won't graduate at all and you can register as a 3rd year student. If your CA at the end of next year is a 6 and all your degree requirements are met, then you will graduate with an honours next year. This will definitely mean some hard work and some extra courses though.

Otherwise you should go see a counsellor as Starfish suggested

Is it your average for the year that's going to be below a 5 or your CA? I was worried about this myself and I originally didn't realize that it's the CA for year 1-3 that matters, not the average for this year alone.

Go see an advisor. You may be able to get permission to be put on academic probation. So that if you meet the 6.0 and higher at the end of your 4th year, you can graduate with honours.