If it’s cow corn the tassels will be browning and receding, pull down the surrounding leaves covering the corn cobs and look at the kernels.
When the kernels look swollen and indented like your molars, expect the farmer to harvest shortly, especially just before a pending rain storm or just after it with clearing weather…If you snooze on this, all you find is leftover stalks after they run the harvester through !
Up in New England that process has been going on for at least a week or two.
Good luck!