The importance of keeping your soil moist
When ever I install a new garden, I make sure the owner knows to keep it moist all the time.
Particularly during hot weather. The reason is there is an entire microbial colony living in the soil, and they need moisture to live. If your soil dries, it may even become water resistant which means your soil would need replacing.
So in hot weather, hand water your garden rather than let it dry out.