1.
~ (on / in sth) ( of a feeling or sth in the air ) to be very noticeable in a particular place in a way that is unpleasant :
Smoke lay heavy on the far side of the water.
Despair hangs heavy in the stifling air.
2.
~ on sb/sth to cause sb/sth to feel uncomfortable or anxious :
The crime lay heavy on her conscience.