Rainbow Mulch does not get any more hot than most other materials outdoors during intense heat. In fact, because it is rubber and does not conduct heat, the mulch under the surface is cooler than other types of material.
However, rubber mulch does create insulation. This is a benefit when used in gardens, since the insulation helps warmth-loving plants to thrive. Because the mulch absorbs heat, the roots of your plants are more protected on those hot summer days. And in the winter, the rubber insulates the ground against cold and snow, and does not retain water or freeze.