More than 111 people have died across six counties after flash flooding from heavy rain began affecting the state last week.

Here's what to know about the deadly flooding, the colossal weather system that drove it and ongoing efforts to identify victims.

Flooding is the deadliest natural disaster facing Oklahomans, a threat far greater than tornadoes. In the United States, flooding kills an average of 103 people a year. Tornadoes, however, caused 48 deaths on average during the same period, according to the National Weather Service.