Melbourne's skyline will be blanketed in a thick haze again on Monday, with experts saying smoke is being pushed towards the city from the East Gippsland fires once more.

The city's air quality was considered "moderate" on Sunday, as 20 fires burnt in Victoria's north-east, but will drop significantly on Monday.

The Environment Protection Authority's state agency commander Marleen Mathias said while air quality remained "pretty good" across the state on Sunday, it wouldn't last.

Air quality in East Gippsland will drop to "hazardous" levels on Tuesday and Wednesday, after being considered "very poor" on Sunday.