Super fog forms when a mixture of smoke and moisture released from damp smoldering organic material such as brush, leaves and trees, mixes with cooler, nearly saturated air. Visibility is lowered to less than 10 feet. Under light wind conditions, super fog meanders through low terrain areas such as creek beds or drainage ditches. Super fog can be very dangerous when present over highways, and has been the cause of several large, multi-vehicle pileups.