The best time for installing a drainage system is typically in the spring or fall when the ground is not frozen. This allows for optimal soil conditions and minimizes disruption to your landscaping.
In the spring, the ground has thawed and is softer, making it easier to dig and install the drainage pipes. This also gives the system time to become fully functional before the heavy rains of the summer months. In the fall, the ground is still relatively soft, and the system can be installed before the winter freeze, ensuring it's ready to handle the spring thaw and heavy rainfall.