If the weather were a lot colder, today's lunch would have been more like an ad lib minestrone, but since temperatures are heading into the 90s*, it's an ad lib salad.
In either case, it would be made with ingredients on hand... In fact, not long ago I did make an impromptu minestrone, using some frozen tomato sauce, leftover vegetable stock, almost-shriveled mushrooms, some potatoes, onions and carrots, herbs and a handful of lentils.
Today's hot-weather version of "cream of bottom-of-the-refrigerator" featured chunks of fresh tomatoes, slivers of red onion, some cut-up yellow pattypan squash, half a sliced cucumber, herbs, salt, pepper, vinegar and oil. Oh, and about four slices of day-old pugliese bread from Artisan Bakers in Sonoma (look for it). I hacked up the bread, leaving the crusts on to soak up the juices in the bowl, and let it sit for about 10 minutes before serving.
Looks like I'm not the only one thinking about food in this form now. Oh, there are lots more of us, too; just go look here. And we all do it a little bit differently. Kinda impromptu.
Go make one yourself, any old way you like.
*Because it IS hot, and it's getting hotter. It's our own fault.