Small amounts of pollen may be seen on the trap from August and the pollen season may extend to April in some years but the major peak of grass pollen is usually seen in October/November with a smaller summer peak around January/February.
From Beggs PJ, Katelaris CH, Medek D et al. Differences in grass pollen allergen exposure across Australia. Aust NZ J Public Health. 2015; 39:51-55