On June 15, 1991, Mount Pinatubo, just 20 miles (32 km) from Subic Bay, exploded with a force 8 times greater than the Mount St. Helens eruption. Day turned to night as volcanic ash blotted out the sun. Volcanic earthquakes and heavy rain, lightning and thunder from Typhoon Yunya passing over northern Luzon made Black Saturday a 36-hour nightmare.