This is applicable to pretty much every 4 stroke engine.
Here is how you should warm up your car or motorcycle, no matter the weather. Start the vehicle, put it in gear, and drive right away. You should not "warm up" a 4 cycle engine. During the time that the motor is started and oil reaches operating temp, extreme care should be given to limit engine rpm. I shift at 4,000rpm on my bike, and 2,000 in my cars while they are coming up to operating temperature. Throttle percentage doesn't particularly make a difference, so long as rpm is limited.
Cold idle is the most wear-inducing rpm point on an engine. Even when outside temperatures are 100 degrees, oil is still not even halfway to the temperature where it is made to perform at. Idle is also a particularly hard rpm for engines. They are out of balance and run rough, there's no load, and worst of all, oil flow and pressure is too low. The two worst things for en engine, idle and cold oil, and we're going to let the engine sit in this state for 15 minutes?
That's not even accounting for the other reasons. It wastes gas, it's illegal, bad for the environment, raises risk of theft, and annoys your neighbors.
By driving the vehicle right away, we put a load on it, and get the rpm up a little, which increases oil flow and pressure. The loading also creates heat, bringing the engine up to temperature quicker.
For automatic transmission cars, after cold start one should wait until the engine rpm settles to normal idle before putting it in gear. This shouldn't take more than 30 seconds. Shifting from park to drive at 1800 rpm on a cold transmission is not something conducive with longevity. Once rpm settles to a normal idle, drive right away, again taking care to limit engine rpm.
Next I'll be going into parking brakes, and after that changing driving habits for better gas mileage.