Do you have a feeder out? No matter how hot it gets, hogs still need to eat. Setting up near some sort of water source is always a good bet when it's hot but like you said, most of them dry up when the rain is lacking. I haven't had any issues with finding the hogs here but they do seem to be sluggish on the hotter days. The area I hunt is swamp land though, so they always have somewhere to go cool off when they want to.

You could put out some feed or a feeder and set a trail camera on it. Then you can see when they are coming and going. I like to set the feeder to go off first thing in the morning and then 10 hours after that. About 4PM. And I set it to be pretty liberal on the feed. I leave it like this for about a week to get them comfortable and therefore complacent. Then I switch it up to where it goes off every 5 hours after the first feeding and the amount of feed distributed is a lot less. Like 2 seconds worth each time. That will cause them to come out during the day to eat out of fear that they won't get any unless they come early. Sometimes they will come just by the sound of the feeder going off. This works especially well if you have other animals showing up for the feed also. Like me, I have coons, turkeys, and crows that come to the feeder. It seems to me like the hogs get pissed and come early to eat before the other critters can get there.