The fishing can be very good below the TMA. However, it's going to be some time before the Housatonic is fishable again. Trout fishing will begin again when you get a few nights with lows in the low 50's and highs in the low 70's. I have heard numerous reports of dead fish floating everywhere. The good news is that they are mostly larger stocked rainbows. I hope that the nice brown trout make it through.
So the simple answer to when is to keep checking the weather for a forecast of cooler weather.