Flash returns for season 2 on Tuesday night, so we'll be hearing about ratings again very soon. Last season Flash was the highest rated show on the CW, and arguably the most successful show in the history of the network by certain metrics. It would take a total collapse for the show not to be renewed, and I don't think we have to worry about that. Last season the show averaged a 1.44 rating, with a season high of 1.90 and a season low of 1.27. You can check out its season one ratings here: http://tvseriesfinale.com/tv-show/the-flash-season-one-ratings-34271/ Anything above a 1.01 average this year would still likely make it the top rated show on the network. To get cancelled it would have to likely fall below a 0.60, which is extremely unlikely. A 1.90 to match last season's premiere seems unlikely to me, as that was the best rating the network has had since The Vampire Diaries premiered way back in 2009. Anything above a 1.5 would be a big success for the premiere, while anything under a 1.3 could be worrying. I'm predicting a 1.7 myself, but we'll find out on Wednesday. If it does indeed get renewed for season 3, which is very likely, syndication economics all but guarantees a fourth season as well. So a decent first half for Flash ratings this season pretty much secures us another 45+ episodes.