Warmer temperatures will likely exacerbate grass pollen levels across the state's north, according to leading expert Dr Edwin Lampugnani.
The grass pollen forecast for the state's north, northeast, Mallee and Wimmera is "extreme" today, while the east remains on "high".
The south-west is moderate, while Melbourne remains low.
Each year Melbourne usually experiences hay fever season in November, and the state typically experiences about 20 high and extreme grass pollen days during the season.
Experts however said the 2023 season is already shaping up to be a "particularly challenging year for hay fever and asthma sufferers" due to how early it commenced.
"By this time in 2020, there had been five high grass pollen days, whereas 2023 has already seen nine, marking the earliest start in the last 30 years," Associate Professor Ed Newbigin said.
Forecasts predict high-to-extreme grass pollen levels across northern Victoria tomorrow and by Monday a statewide forecast of extreme grass pollen levels is anticipated.
These conditions are expected to persist through to at least Thursday.
The forecasting system enables people who have asthma or seasonal hay fever – and who are at risk – to plan ahead and reduce their risk.
