Air quality in Melbourne has taken a hit from a cocktail of bushfire smoke haze, fog and low cloud.

The Environment Protection Authority said air quality in Melbourne dipped to "moderate" overnight and will probably drop to "poor" on Friday.

At 10am on Friday Melbourne sat under a thick blanket of smog. Credit:Justin McManus

The EPA had earlier forecast for "moderate" pollution, but escalated the warning to "poor". Saturday is expected to remain at "moderate".

The Bureau of Meteorology said easterly winds could keep pulling smoke across from East Gippsland for days, possibly into next week.