If a thunderstorm hits the airport, they shut the place down as if they'd never expected anything like that would ever happen.
The Cathedral Basilica was well worth seeing, a 20C church covered with mosaics and otherwise with the aesthetic principles, just not the artistic style, of a Byzantine basilica.
At Grant's Farm, you can ride on a tram through the deer park and see the deer, elk, and bison without having to walk around in the sweltering heat. Baby bison are unexpectedly cute.
There's a section of town where all the noted Italian restaurants are. I won't say the good ones, because the one we ate at was more emphatically old-school than it was good. If you want a lunch heavier than a full dinner, this is where you go. You might get better Italian at an informal family-style sports bar place in the suburbs.
The quality of toasted ravioli, St Louis's culinary specialty, varies tremendously depending on where you get them. Nor did I have success with the local barbecue.
On the other hand, you don't have to go where it was invented to get a good concrete, which is what they call an extra-thick frozen custard.
There's also something called "trashed wings." Apparently these are chicken wings with the sauce baked on. Despite the name, I like it that way.
For a preserved slice of what a town here looked like in the early 19C, go across the wide Missouri to St Charles. The shops probably didn't sell boutique olive oils back then, though.
Air conditioning is your friend.