Precise temps for overseeding?

[sulston]

OK I know late summer/early fall is the best time to do any overseeding but I was just wondering if anyone knows specifically what kind of night/day air or soil temps are ideal to start my aerating/topdressing then overseeding. The grass here in Southern ON, Canada has been dormant pretty much since June, we've had no rain and hot hot temps so since the weather seems to be so F#@$ed up these days, I'd like to know a little more specifically when the conditions are best, rather than going by the seasons because they just aren't consistent anymore. Thanks for any advice.

[echeandia]

My understanding is that when the temperature is below 80 F grass will germinate.