Question
Will you please explain what the watering schedule should be for overseeding winter rye grass?

Answer
A seed soaks up water which causes it to swell and burst its seed coat. The plumule grows upward out of the seed to become the shoot and the radicle grows downward from the same area to become the root of the seedling. Both plumule and radicle get their first nourishment from the material contained in the cotyledon(s) of the seed. You can imagine that these processes call for a lot of energy and water is what jump starts this processing and keeps it going.
Now everything has to be in proportion. The seed itself is small and can be moved by water or even washed away. Plumules and radicles are very small and tender. They can be easily trampled to death or again - washed away. The tiny roots struggle for anchorage while the tender shoot stretches to reach up into the light. The water has to be present throughout the 7 to 14 days in just the right amount for the seedlings to become self sustaining. When it becomes necessary to supply water, it should be applied lightly and this often means that it has to be done more frequently. How frequently depends upon the soil. Sand dries out more quickly than a loam. If the weather is hot, water will evaporate faster from the soil surface. So it depends and you are thinking that I am being evasive. Not really. It might sound complicated but if you can visualise what is taking place at ground level and if you probe the soil daily to judge the moisture level and while you are down there, you look keenly around to see what is going on, you will succeed in raising a good crop of rye.