I popped the hood. It's a lot harder to tell what's going on with a van engine since it's way back in there. But there was no steam, no smell of hot coolant, no chemical mist. The area under the windshield washer reservoir was dry (though the fluid was rather low). Everything looked dry.
I got on my knees, reached under the van and caught a couple of drops. It moved and felt like water. No color, no smell, so it wasn't coolant, engine oil, transmission fluid or washer fluid. By now I was fairly certain it was just water, so I tasted it. Nothing.
Okay, it's water. But why is it dripping from the van?
Cool metal + fog = condensation.