BigMacFu was right about where you are from making a difference.
I spent 17 years working on the Railroad in Iowa, Minnesota and South Dakota. I've worked outside at temps down to -30.
The coldest I rode my bike was -6. It's too hard on the lungs to suck in the air you need when it gets much below -10.
Last year I nearly got myself killed at 10 above. The temp had fallen while at work and I had gotten overconfident in how I was dressing for my 6-mile rural road commute home. I had been wearing just a windbreaker, sweatshirt and jeans and relying on sprinting for the first 1/4 - 1/2 mile to get warmed up.
This night I had a bad headwind that was really making me work to the point of a light sweat. About 2 miles into the ride I had a flat tire. It seemed to take forever to change the flat, the rubber was stiff and so were my fingers. I had the shakes from the wind and my damp clothes by the time I had popped the co2.
When I got back on the bike I just couldn't warm up. I didn't have any energy. I thought about stopping at the farm a mile from my house and calling my wife but I kept thinking, "it's just another mile." Anyway I kept peddling and then I just plain pedaled right into the ditch. I was so disoriented I wasn't paying attention. If there hadn't been some woods to break the wind the last half mile I think I'd have frozen to death.
I'm a lot more careful now.