I'm one of those people who almost always needs a sweater in the evening, so I treasure these summer nights when I can be sleeveless outside. It's hot during the day, but to me it's worth it to have evenings when I don't shiver.
Here's a good way to spend a couple of hours on warm a Sunday evening: the Playhouse District's 6th Annual Free Jazz Summer Concert Series, Sunday nights, 5-7 pm in the courtyard at Vroman's.
I took this photo last Sunday, July 12th. Nick Mancini's Quartet was scheduled, but this was definitely a trio. So if you're particular about which group you're going to see I recommend you give a call first (there's a number listed at the link). Otherwise, just go. The music's going to be good, and you'll get to sit outside without a sweater.