How often to aerate?
The common advice here is once every one to three years. The specifics depend a lot on your type of soil. Loose soil doesn't need to be aerated very often. Thick, clay-like soil that easily traps water needs to be aerated more frequently. Especially thick types of grass may also call for aerating more frequently. As a general rule, you shouldn't need to aerate more than once a year at any time ("too much of a good thing" applies here, since you don't want to damage your soil).
When to Aerate Your Lawn: Bracing for fall
Looking for a specific time of year to aerate your yard? Your best bet is probably right before fall, as close to late September as you can. The reason is that aeration is typically followed by overseeding and fertilizing. Therefore, an almost-autumn date gives your lawn several months to absorb the fall rain, let the new grass seed take root, and let the soil soak in the fertilizer before the coming hibernation of winter. This also helps your grass effectively fight against weeds and competitive grasses like crabgrass that you want to avoid in the coming spring of next year.
The Spring Alternative
If you aren't planning on much overseeding or if you have particularly cold autumn seasons and hot summer seasons in your area, you may want to plan on spring aeration instead. The best time here is anywhere between March and June, but preferably sometime in April. Here your goal is similar: Give your grass time to readjust and be ready for the harsh summer and cold fall or winter seasons.
Note that there are several different ways to aerate your yard, including hand aerators, tow aerators, liquid versions, and more. For information on how to aerate your lawn and keep your grass healthy, visit us at Inspect-All Services!