For Los Angeles, etc, it would be good to investigate this: If one had shallow pools of seawater with dark bottoms to absorb solar radiation one could increase water temperatures to more than land temperatures. The second graph is for Cape Town. The upper two curves show sea and land temperatures. The lowest curve (generally) shows the rainfall in mm. The land temperature starts out being higher than the sea temperature and rainfall is low. Then the land temperature is less than the sea temperature and rainfall is high, etc. Third graph is for Los Angeles Basin. Usually high land air temperatures bring in air from the sea. But if land is hotter than sea air then the relative humidity of the sea air will decrease on being heated by the land. Here is a graph for Los Angeles basin. It uses mean sea temperatures and land air temperatures. The rainfall is in inches and the temps are in deg C (not really right to do T and rainfall on one axis, but still), The sea is hotter than land air T up to month 4. Then sea temp is cooler than land air temp up to month 9, then sea is warmer for 10, 11 and 12. Do not know why it works so dramatically in some cases, but it seems generally higher sea temps than land air temps mean much more rain.
Jeddah graph below: The graph shows the sea and land temperatures and (although it in the wrong units of mm) shows the rainfall in mm (bottom curve).The graph starts out with sea temperature being greater than land temperature (and rainfall is relatively high). Later the land temperature is higher than the sea temperature (and rainfall is close to zero). Later the sea temperature becomes higher than the land temperature and the rainfall increases dramatically.