Finally, I figured out that there was a *cold* wind blowing from the heater vent. This was because the control was set to Constant Fan, not Auto Fan. Also, the thermostat was at the night-time setting (57). Thus, the Fan was blowing cold air around!
The heater/AC control is next to A's homework desk. A likes to play with the control. She's famous for turning the thermostat as low as she can during the summer. Apparently, she wanted some wind blowing tonight. And she got it.
