2004 GMC Sierra 1500 Pickup Owner's Manual - Page 110

Windows {CAUTION: Leaving children, helpless adults, or pets in a vehicle with the windows closed is dangerous. They can be overcome by the extreme heat and suffer permanent injuries or even death from heat stroke. Never leave a child, a helpless adult, or a pet alone in a vehicle, especially with the windows closed in warm or hot weather. Manual Windows Turn the hand crank on each door to manually raise or lower the manual windows. 2-16