How does one know when a flow is heavy or light or if there is a flow at all.
			
			
			
				Look for nectar in the hive.  Cells recently filled with thin nectar are a sure sign of a flow.  Lots of cells recently filled with thin nectar and all the bees working heavily is a good sign of a strong flow.  No nectar, a lot of fighting and robbing and grouchy bees are a good sign of a dearth.