I chose -9 to 0°F, only because that's the coldest I've ridden, and it's not really likely to get much colder than that around here. The lake (Lake Ontario) moderates our temperature. If it freezes solid across, then all bets are off.
That is such a rare occurrence that it has actually happened only twice in recorded history, and neither of those winters were within either of our lifetimes.
The real kicker is that you guys usually get more severe winters on the south side of the lake than we do up here.