I am putting mulch around our garden and greenhouse plants to help retain moisture and also reduce the soil temperature.
It gets scorching hot at our homestead during the day. We have sandy soil so it does not hold a stable temperature sort of like in the desert. When the sun shines it gets really hot and at night it gets very cold.
So during the day the plants get over heated and wilt. The mulch should help a lot by keeping the soil temperature down. At night the opposite is needed. The ground gives off its heat in a hurry and then gets cold fast. The mulch will retain the warmth of the day through the night, protecting the plants some.
Also the sun burns off the moisture in the ground fast. After a rain, the soil will be dry in a few hours of sunlight down to a couple feet deep. The mulch should help retain moisture around the plants where it is needed.