It's best to aerate your lawn when the soil is moist, so either after a rain or before you water. If the soil is too dry, the Aerator will just bounce off the ground. You don't need to aerate your lawn every year - once every 3-5 years should be enough.

There is no general answer to this question, as the best time to aerate a lawn depends on the type of soil, the climate, and other factors. However, in general, it is advisable to aerate a lawn when the soil is moist but not wet. Aerating when the soil is too wet can damage it.