This is a fun video to put n "loop mode" and watch.
The states that normally grow lots of corn get more rain in July than the states north and south of them. Corn tassels in July and a good soaking in July adds hugely to the yield.
Eastern Oklahoma and Kansas are wet during the last bit of May, before wheat pushes up seed heads. The extra moisture is stored in the soil for that final push.
Northeastern Tennessee is DRY in October and southeastern Arkansas is dry in mid-August. Presumably the prevailing weather patterns in Southern Appalachia are from the southeast and eastern Tenn is on the leeward side of the Appalachians then.
One of the things that surprised me is that Michigan is just as wet in July/August as it is in September/October. That does not mesh with my mental image. It may be that we get as much rain but the evaporation potential is much lower in the fall.
Also of note, much of the moisture that is pumped out of the Gulf of Mexico tracks west of Michigan. June-through-September has the band of states from Missour-through-Minnesota wetter than Michigan. Those are prime growing months.
Specific to the Lower Peninsula, you can see the effect of a relatively warm Lake Michigan pumping moisture into the air starting in early December. There is a precipitation gradient with more precipitation on the west side of the mitten than the east side.