I worked in MOA for almost a decade. It's very rarely cold in the morning. The place is massive and it doesn't have enough down time to get cold. The coolest it would get would be the morning after Christmas. Winter and empty for over 24 hours. Perfectly warm by noon. The amount of lights and electricity on top of body heat, ovens and grills from restaurants and the food courts, the heat from the rides, the sun coming through the skylights... It's more than enough to keep things warm for a long time.