The best time to aerate depends upon the type of turf. Aeration should occur during periods of active growth, to help with the recovery. Typically, warm season grasses are aerated in late spring and early summer. The ideal time to aerate cool season grasses is early fall, but they can also be aerated in spring. Aeration should always be done before application of pre-emergents.
Aeration should be avoided at certain times. For example, cool season grasses should never be aerated during times of high stress (summer). Warm season grasses should not be aerated preceding dormancy (fall).