Fall seeding is usually best. In Utah, it can be difficult to pick a time when it has cooled enough and there is still time for the seed to germinate before the first snow.

Some people dormant seed. To do that, you seed after it is too cool for the seed to germinate but before the lawn is covered with snow. The winter snow and the freeze/thaw cycles will carry the seed into the ground. The seed will then germinate in the spring as soon as it warms enough (probably earlier than if you seeded in the spring). It may be able to take enough advantage of spring snowmelt and rain that you won't need to irrigate.

If you dormant seed, you won't be able to use a pre emergent.

Corn Gluten meal can't tell weed seeds from grass seeds.

If you plan to overseed in the fall- say September 15th- what is the latest you could put down CGM in the summer?

In other words- how long do any pre-emergent qualities last?