April 1
1945: The Regional Meteorological Centre in Chennai, India, was formed.
April 2
1957: The first day of a 4-day tornado outbreak struck Texas and Oklahoma, including a tornado that caused severe damage and killed 10 people in the Dallas–Fort Worth metroplex.
April 3
1974: The Super Outbreak, one of the most severe tornado outbreaks in world history, spawned 148 tornadoes, including 30 violent tornadoes, in the east-central United States and Windsor, Ontario, Canada. More than 300 people were killed, and $3.5 billion (2005 USD) in damage was reported.
April 4
1978: Cyclone Alby, the most damaging tropical cyclone to impact Western Australia on record, brought widespread damage to homes and crops and wind gusts as high as 150 kilometres per hour (93 mph) in Albany.
April 5
1815: Mount Tambora began the largest volcanic eruption in modern history, eventually causing the Year Without a Summer.
April 6
2020: Cyclone Harold, one of the strongest tropical cyclones in history to strike Vanuatu, made landfall on Espiritu Santo with 10-minute maximum sustained winds of 115 knots (215 km/h; 130 mph).
April 7
1999: Cyclone Gwenda reached peak intensity near Western Australia, with a central pressure of 900 millibars (26.58 inHg), making it tied for the strongest cyclone ever observed in that region.
April 8
1984: Cyclone Kamisy, the worst tropical cyclone to affect northern Madagascar since 1911, reached peak intensity as it approached the island, with wind gusts as high as 250 kilometres per hour (160 mph).
April 9
1947: A tornado or series of tornadoes plowed through several towns in Texas, Oklahoma, and Kansas, killing 181 people.
April 10
1996: A wind gust of 408 kilometres per hour (254 mph) was measured by a weather station on Barrow Island, Western Australia, as Cyclone Olivia made landfall. As of 2020 this remains the highest wind gust ever reliably measured.
April 11
1965: The Palm Sunday tornado outbreak, one of the worst in history, produced 78 tornadoes and killed almost 300 people in the American Midwest.
April 12
1934: A wind gust of 231 miles per hour (372 km/h) was measured at the Mount Washington Observatory atop Mount Washington, New Hampshire. At the time, this was the fastest wind speed ever recorded, and it remains the fastest surface wind speed ever measured outside of a tropical cyclone.
April 13
1994: The GOES 8 weather satellite was launched. Part of the Geostationary Operational Environmental Satellite program, GOES 8 would provide weather forecasting data to the United States until its retirement in 2004.
April 14
1999: A severe hailstorm, the costliest disaster in Australian history, dropped hail stones 9 cm (3.5 in) in diameter across the Sydney area. The storm caused more than A$ 2 billion in damage and injured 50 people.
April 15
1927: In New Orleans, 15 inches (380 mm) of rain fell in 18 hours, worsening an already historic flood and leading to the fateful (and ultimately unnecessary) decision to intentionally breach a levee south of the city.
April 16
2011: The final day of a three-day tornado outbreak brought dozens of tornadoes to the Mid-Atlantic and Southeastern United States, killing 26 people.
April 17
1979: Flooding along the Pearl River in Jackson, Mississippi crested at 43.28 feet (13.19 m), exceeding the previous record by more than 5 feet (1.5 m).
April 18
2014: An avalanche killed 16 Sherpa guides working on Mount Everest.
April 19
2000: Cyclone Rosita, one of the strongest tropical cyclones ever to strike the Kimberley region of Western Australia, reached Category 5 intensity (Australian scale), making landfall just after midnight near Broome.
April 20
2004: A strong tornado, part of a surprise outbreak of 29 tornadoes, killed 9 people in Utica, Illinois.
April 21
1965: A devastating tornado outbreak killed 58 people near Chicago.
April 22: Earth Day
2011: A nighttime tornado, caused major damage in parts of St. Louis, Missouri, including Lambert-St. Louis International Airport, but amazingly caused no deaths and few injuries.
April 23
1792: John Thomas Romney Robinson, inventor of the cup-anemometer, was born in Dublin, Ireland.
April 24
1908: One of the deadliest tornadoes in US history killed at least 143 people in Louisiana and Mississippi.
April 25
1994: An F4 tornado killed three people on the first day of a 3-day tornado outbreak.
April 26
1998: Cyclone Alan which had been impacting French Polynesia with several days of strong winds and heavy rain that killed 10 people, dissipated west of Tahiti.
April 27
2011: The deadliest American tornado outbreak in 76 years killed more than 300 people in the Southern United States.
April 28
2002: As part of a larger tornado outbreak, a violent tornado struck the town of La Plata, Maryland, killing 4 and injuring more than 100 people. Initially rated F5 on the Fujita scale, which would have been the strongest tornado on record in the Eastern United States, the tornado's rating was later revised downward to F4.
April 29
1991: The second-deadliest tropical cyclone in world history struck the Chittagong area of Bangladesh, killing at least 138,000 people.
April 30: End of the Southern Hemisphere tropical cyclone seasons except for the Mauritius and Seychelles region
1924: Dozens of deadly tornadoes killed 111 people across the Southeastern United States, including one F4 tornado which killed 53 people in South Carolina over a 105-mile (169 km) path.