Cooler temps also keep my mg blossoms open longer. I noticed this a couple of years ago. This year's mg is a volunteer that I trained on a small obelisk. Each evening or two I cut off the spent blooms to keep it from seeding. I expect some seeds to escape my notice so may have a few volunteers next spring anyway.

This afternoon I saw a hummingbird trying several mg blossoms but they had all collapsed from the morning thunderstorm.

Yes, saw this scene "out in the wild" yesterday about 2:30 PM. It was hot, about 88, but lots of clouds, mostly "shady" day.

Some other mixed Ipomeas in the wild, still mostly open mid-day. More pics of these here if interested in peeking.