Try contacting your local county extension service for help and advice. They will know more about conditions in your area and your specific crop/variety and should be not just willing, but eager to help you.

If the plants are dry and brown, you might as well harvest. Once the kernels show the dent, all that's left to do is get them into a warm dry place to finish drying. so they can be used.

Steve

I let them dry on the stalk until the husks are brown and then a while longer.

Frost doesn't hurt them at all, but there are numerous animals that will eat, or at least gnaw the kernels. The longer they are out the more likely to be discovered.

I take some starting about now and make super-fresh cornbread.

Sounds good -- like I've got some leeway.
Thanks!