Are there no signs of life at all? Geraniums can usually take quite a bit of heat as long as they get enough water. Most do NOT like full, all-day sun, and will show you by getting ratty looking leaves that brown around the edges. You can try digging up the plant carefully and examing the root system for signs of life. Otherwise you just have to wait for cooler weather and see if the plant starts to re-grow its leaves. In any case, keep it well watered, but don't drown it.