Are you growing them in full sun or can you give them a bit of light shade in the hottest parts of the day? How often are you watering them when the temps are that high (provided it is not a type that is summer dormant)?

I'm at the other end of the temperature extreme (often 60 degrees in the summer) but I was growing some Titanopsis seedlings in small plastic pots on a black weed suppressing cover in the hottest, sunniest spot on my yard and pretty much watered every day during most of the summer.

C,

I grow Mesembs but my climate is nothing like Texas so my experience won't help much. I know that Lithops have long been referred to as windowsill plants and I'm sure many people are successful with south-facing windows. I haven't tried any Lithops indoors but of the various Mesembs I have tried, Glottiphyllum does great, a vigorous and thirsty plant that doesn't require more than a window can offer.

I've seen the lengths that are necessary to really grow Mesembs in an extreme environment like yours. We're talking about a closed greenhouse with a heater in the winter, windows and a door you can open in the summer.

Otherwise, there are a handful of Mesembs that mights tolerate window/sun room conditions. I've found that many of them really need the heat and strong light to properly absorb old leaves. A plant like Mitrophyllum might do fine in low light until after summer when its leaves should have been dried up by the sun and instead are juicy, limp and too thick for the soft new leaves to break through.

Well, I popped in here and got myself wrapped up in a Mesembyryontification. It's my bedtime. Goodnight interwebs.