The spasm of storms that surged through 12 southern states in late April generated 305 tornadoes between April 25 and 28, the National Oceanic and Atmospheric Administration estimated, the largest number ever recorded in connection with one weather event.

The outbreak surpassed the previous record of 148 tornadoes which occurred from April 3 to April 4, 1974, NOAA said in a statement.

The 24-hour period between April 27 and April 28 this year was also among the deadliest for a one-day tornado cluster. Approximately 318 people died from tornado-related causes, ranking it the third deadliest day behind more severe storms in 1925 and 1932 which resulted in 747 deaths and 332 deaths, respectively.

Five states—Mississippi, Alabama, Georgia, Tennessee and Virginia—were hit with 20 or more cyclones each.

One tornado, 1.5 miles wide and 80 miles long, ravaged Tuscaloosa and Birmingham, Ala. leading to 65 fatalities, the most deaths in a single tornado since a 1955 twister killed 80 in Kansas.

Jane Lubchenco, administrator for the NOAA, said she personally witnessed the damage of the colossal tornado in Alabama

“The damage is heartbreaking,” she said in a statement. “The human stories are both tragic and heroic.”