Idle jumps from ~650 to ~1000 at cold start

[kylek350]

2001 CC LB SRW XLT Automatic, 95k. I'm still pretty new to this truck, but I've notice this happen about three times now. When cold starting (e.g. after sitting overnight) and idling for a minute or so, the idle RPM jumps from about 650 up to 1000 and stays there until I touch the brake pedal; then it returns to 650. This only recently started happening (that I'm aware of). A couple things come to mind:

1) I recently had two recall items taken care of at the local Ford dealership: Cam Position Sensor and Speed Control System Modification. Could one of these two be causing this behavior?

2) I live near Chicago and it's getting colder (approaching freezing overnight). Could this be happening by design to aid in cold starting situations?

[russf]

Its normal