What is the largest derecho on record?

• By path length: the 1999 Boundary Waters (BWCA) derecho, ~1,300 miles, the longest tracked derecho path on record.¹NOAA Storm Prediction Center, "The Boundary Waters-Canadian Derecho," spc.noaa.gov, accessed September 2026. https://www.spc.noaa.gov/misc/AbtDerechos/casepages/jul4-51999page.htm
• By spatial extent (dual-line event): the April 4-5, 2011 serial derecho, two simultaneous lines that at one point stretched a combined 800+ miles, generating 1,096 wind reports (a record at the time) alongside 46 tornadoes.²NOAA Storm Prediction Center, "The Southeast U.S. Derecho of 4 April 2011," spc.noaa.gov, accessed September 2026. https://www.spc.noaa.gov/misc/AbtDerechos/casepages/apr042011page.htm

Sources & References

• 1
  NOAA Storm Prediction Center, "The Boundary Waters-Canadian Derecho," spc.noaa.gov, accessed September 2026. https://www.spc.noaa.gov/misc/AbtDerechos/casepages/jul4-51999page.htm
• 2
  NOAA Storm Prediction Center, "The Southeast U.S. Derecho of 4 April 2011," spc.noaa.gov, accessed September 2026. https://www.spc.noaa.gov/misc/AbtDerechos/casepages/apr042011page.htm