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