How do you convert liters/sq meter to inches of rainfall?

Over here, on the Mediterranean coast of Spain, we experience a weather phenomenon called a "gota fria", literally a "cold drop" It usually happens in October, after a particularly hot summer, such as this past summer. During this cold drop, the quantities of rain are HUGE, often washing away bridges, highways and rail lines and flooding whole towns and villages. If anyone out there can help with the conversion to inches of rain, I would be grateful. Thanks