To keep a rabbit hutch cooler in the summer, it is recommended to use light-colored or reflective tarps. Light-colored tarps, such as white or light gray, reflect more sunlight and heat compared to dark-colored tarps. This helps to prevent the hutch from absorbing excessive heat and keeps the interior cooler.

Additionally, using a shade cloth or mesh tarp can provide airflow and ventilation while still offering shade and protection from direct sunlight. These materials allow air to circulate through the hutch, preventing heat buildup.

It's important to ensure that the tarp is securely attached and doesn't obstruct the airflow. It should be properly positioned to provide shade to the hutch without trapping hot air inside.

Remember, along with using a suitable tarp, other measures such as providing ample shade, proper ventilation, and access to fresh water are also important to help rabbits stay cool during hot summer months.