CMO = Cool Morning Openers?
In addition to cold nights, daylilies seem to resent wide swings between day and night temperatures. Even in the spring and fall, with nights in the low-mid 50's, they open fairly reliably, which I suspect is because the days are moderate as well. Naturally, much of the "fanciness"—fringing, patterns, eyezones—is muted, but they at least open correctly, and the colors are rich.
The real problem daylilies have here on the west coast seems to be the type of evening they have, rather than the overnight low. The temperatures tend to fall below 60 soon after sunset, and then every type of difficult opening can be seen the next day. Forty miles inland, it might still be 75 degrees at midnight, followed by a slow decline to 60-65 by morning. This gives the bud plenty of time to develop fully in preparation for bloom, and the flowers have more of a normal appearance.
Ken
East S.F. Bay Area
USDA Zone 9
