So just how slippery are these tires in the cold? In Calgary here, we don't really have any snow on the ground/roads, but it has been between -15 and +3 degrees C for the last couple weeks.

The reason I ask - I am planning on getting winter tires when my car arrives, but should have them ready to go beforehand? Or will I be able to survive for a week or two on the summer tires.

I have heard that the rubber isn't the greatest once temperatures drop below freezing...

 

yes summer tires harden up when it gets cold and snow tires are made from a softer rubber.

 

So am I going to slide out and crash if I'm on those tires at -5 deg. C? Or will I be ok so long as I take it easy? haha

 

If there is zero moisture on the ground, you'll probably be okay as long as you decrease your speed, but if its below 40 and wet, you are asking for an accident sooner or later.

 

Is it THAT dangerous driving in rain with 19"s? Unless you go 10-20 mpg less speed limit.

 

When the temps are near freezing, yes.

 

I would replace them with some good all-season tires when you can.