Pretty sure I found the answer to the question that I asked. This table (see image below) comes from page 6 of the PDF that is linked below. The calculation for optimum EMC can be obtained by:
1. Finding the EMC for the highest RH and temperature
2. Finding the EMC for the lowest RH and temperature
3. Determine the midpoint of those two EMC values. That's optimum EMC for installation.
It may not be possible or reasonable to achieve the optimum EMC so you may have to do other things to compensate.
https://www.fpl.fs.fed.us/documnts/fplrn/fplrn268.pdfFeel free to send a private message if I may be able to help you.