What really happens in this picture is this: land heats up faster than water. When the sun comes out, the land heats quickly, forming an area of low pressure directly on the island. This results in an area of higher pressure offshore.
Since air moves from high to low pressure, the marine moisture as well as moisture from the island gets drawn into the low pressure over the island. Low pressure creates upward vertical movement, causing the warm moist air to rise, cool and condense into a cloud directly over each island.