Port Renfrew is situated at the base of the San Juan Valley, a diverse area of forest, rivers, lake and wetlands, which runs Northeast from the Straight of Juan de Fuca along a geological faultline.

The San Juan and Gordon Rivers converge just north of Port Renfrew, just south of where the Straight of Juan de Fuca opens up into the Pacific Ocean. Port Renfrew's proximity to the ocean and local high relief creates a mild and wet maritime climate, with an average temperature of 3.2 degrees Celsius in January to 14.9 degrees Celsius in August, and an average 3.6 metres of rain per year, ideal conditions for the rainforest vegetation - including prehistoric ferns and millennia-old trees - that thrives in the area.