Question
I chose rebel elite and had a rainfall of 12 inches in 8 hours.  the rain took my seed and my loosened topsoil.  It is late October in south east virginia, and the average temperatures are 45 lows and 65 daytime highs.  

bottom line: How low of temperatures will these tall fescues germinate in?

Answer
Soil temperatures cool more slowly in fall and are slower to warm up in spring. Therefore, even with the temperatures you have now, the soil temperatures will be buffered and allow germination. It may take 21-30 days to germinate with the current temperatures. It will take 1/4 of that time in late August.