Heat from an object that weighed probably will result in a floating hot air and cold air will flow over. The stream of cold air pushes the object up. Make an object weighing less than the actual value.
The heat from the object to the scale may result in a hot air floating upward. And the colder air will flow in to replace. A stream of cold air will push up the object. Making objects weighing less than the actual value.
The heat from an object weighing may result in a hot air floating up high. And the cool air to flow into the place. A stream of cold air will push up objects. The weighing objects less than the actual value.