Thanks, Steve.
What is a good rule of thumb for conditions before the time a course closes for overseeding? Will it be very dry and brown (may or may not be a bad thing) for a couple weeks before (getting progressively drier up to the day it closes)?
Depends on the course and the budget. Yes, it will be getting dry and brown. Some courses will start scraping/scalping even while play is still open so if you're planning to play in the week or so before a course closes for overseed, it's a good idea to give a call and find out what they do to prep the course prior to closing.
If they aren't scalping, then late September is often a great time to play in Arizona. Courses are as dry as you'll ever find them and the weather is ... tolerable.