National Climatic Data Center (April 2011). "April 2011"(PDF). Storm Data and Unusual Weather Phenomena with Late Reports and Corrections. 53 (4). Asheville, North Carolina: United States National Oceanic and Atmospheric Administration. Archived from the original(PDF) on February 8, 2015. Retrieved February 8, 2015.
National Climatic Data Center (April 2011). "April 2011"(PDF). Storm Data and Unusual Weather Phenomena with Late Reports and Corrections. 53 (4). Asheville, North Carolina: United States National Oceanic and Atmospheric Administration. Archived from the original(PDF) on February 8, 2015. Retrieved February 8, 2015.