Hello Geoff, they way I handle my Adeniums here, once it is awake, I start to water, doing it early in the day, so it has time to fully drain out the rest of the day. On the onset, I do it in intervals, since the plant is still waking up slowly and then I reposition them to more full sun since it likes that more.
If forecast temperature is expected to be very high like 85F to 100F ++ (29C to 37C++) I step up watering, doing it everyday. I do not know of your humidity levels there during summer time nor if you have summer rains. In my area we go very dry ( 0 to 30% humidity), no rain, for about 6 to 7 months, so it is imperative for me to water my Adeniums often, by then our temperatures area also soaring high into the triple digits. Adenium is one plant that can take in the most heat and direct sun it can get, so it is my least worry during the peak of summer, but it needs to get watered everyday when it gets into that onerous dry and hot conditions. That is why my Adeniums are in shallow but wide containers, so it helps as well in faster dryout time at root level.
Make sure your soil/media is very gritty and well draining. Although it enjoys frequent watering during high temp days, that media needs to be well draining, so the roots are not sitting in a water logged container.
