Earlier quoted context omitted.
The warmer air over land rises up, cooling in the process. But then water in it condenses and gives up heat, that supports the upward flow. So it's kind of runaway process. Eventually when there's too much water condensed, then it overcomes the upward flow and rains down. How it happens, and whether it happens at all, whether the rain won't evaporate in midair etc. depends on variety of conditions.
Ohhh that makes sense. And since they are so close to water, there is always an amount of humidity in the air too I suppose. Thank you for the explanation!
Dubai is on the coast too, though. So there's something else going on. My guess is the dry sand might be a moisture sink and vegetation itself often puts out and collects a lot of humidity, but there's not as much around in Dubai.