Preliminary estimates from the government say that 312 tornadoes formed and 344 people were killed during the outbreak of severe weather between 8 a.m. ET on April 26 and 8 a.m. ET on April 28.
The estimates from the National Oceanic and Atmospheric Administration (NOAA) show that the majority of the tornadoes, 226, formed during the April 27-28 time frame.
NOAA says the tornado outbreak was the deadliest in a two-day period since April 5-6, 1936 when 454 people died in Tupelo, Mississippi, and Gainesville, Georgia. The deadliest single day for tornadoes was March 18, 1925 when 747 people were killed across seven states.
The Nation Weather Service (NWS) estimates that there were more than 600 tornadoes in April, besting May 2003's 542 for the single month with the most tornadoes.
The NWS says that year-to-date numbers show 881 tornadoes have been formed so far this year. The yearly record is 1,817, set in 2004.