Core aeration should be performed in the early fall for cool-season grasses and in the middle of spring to early summer for warm-season grasses. Aerating when grass is at its peak growing season works the best.
Compacted soil is a problem for many lawns due to excessive traffic, and aerating is a good way to deal with this issue. During core aeration, a lawn aerator machine removes cores from the soil and thatch from the lawn. High-traffic lawns should be aerated every year or two. For lawns with little to no traffic, aerating every three to five years is enough.