Is the 2018 grub season expected to b e mild or bad this year?
There is simply no way to make that prediction, particularly at this point in the season. In fact, I contend "grub predictions" in general are about as accurate as predictions of fall color. There are simply too many factors that can wreck the predicted outcome.
First, keep in mind that white grubs are the larval form of scarab beetles and the three most common grub-producing beetles in Ohio are Northern Masked Chafers (Cyclocephala borealis), Southern Masked Chafers (C. lurida) and Japanese Beetles (Popillia japonica). You only have the northern chafers in your part of the state. However, these beetles as well as Japanese beetles are just now emerging, so we don't yet know if there will be high numbers of adults to lay eggs or low numbers.
The next challenge is that masked chafers and Japanese beetles lay dehydrated eggs that must absorb water from the soil in order to develop, so wet mid-summer soil conditions that supports a greater egg hatch could mean more white grubs. However, summer rains can be spotty meaning conditions can be different under turfgrass just few miles apart. Also, irrigated turfgrass presents a different outcome which is why we typically find more grubs under irrigated turf.
White grubs must also run a gauntlet of pathogens, predators, and parasitoids. Survival to pupation is not a sure-fired proposition even if egg hatch was highly successful. So, even if there are a large number of adults flying, which we don't know yet, and we have adequate summer rains to support egg hatch, there is no guarantee large numbers of white grubs will survive to be an issue.