| June 2007 | Flash Flood | Marengo | $750,000 | Eight to 12 inches of rain fell in the Marengo area, causing widespread major flash flooding throughout town. Water covered numerous roads, closing them or making them completely impassable. Some homes were surrounded by water up to 3 feet deep. The National Guard was activated to pump water from the town. Due to incredible local run-off, the Iowa River in Marengo rose from 11.4 feet to 17 feet in just 5 hours. (Flood stage is 14 feet.) The river eventually crested at 17.46 feet the morning of the 23rd. Some residents described the flooding of the town as worse than 1993, and in fact worse than had been seen for more than 40 years. |
| June 2009 | Flash Flood | Marengo | $250,000 | Heavy rains have resulted in flash flooding of several streets in Marengo, IA during the evening of June 21 and early morning hours of June 22. Flood waters were 8 to 12 inches deep. |
| June 2010 | Flash Flood | Marengo | $100,000 | Heavy rains resulted in flash flooding in Marengo, IA during the morning of June 23. Streets were full of flood water and sewers were bubbling over. In addition, major street flooding with water 12 to 14 inches deep was observed about 4 miles north of Marengo. A trained spotter also contributed to this report. |
| June 2009 | Flash Flood | Marengo | $50,000 | Heavy rains resulted in flash flooding of one lane of Highway 6 in Marengo, IA during the late afternoon and early evening of June 19. |
| June 2011 | Lightning | Marengo | $15,000 | Lightning struck a tree which then fell onto a car in Marengo, IA at 130 am CDT June 21. This report was relayed by KCRG-TV. |
| July 2006 | Thunderstorm Wind | Marengo | $15,000 | Trees & limbs down; roof partially off a business |
| May 2017 | Thunderstorm Wind | Marengo | $10,000 | The county emergency manager reported power poles and trees were snapped from Ladora to Marengo. Some of these trees fell on houses and other buildings. |
| June 2007 | Flash Flood | Marengo | $10,000 | A hog farm north of Marengo suffered a severe flash flood. The flood waters washed away and destroyed a hog building with about 100 hogs inside it. Over the next few days, all but 7 of the hogs were recovered alive. Residents described wading into chest-high water in an attempt to save the animals before they were swept away. |
| June 2007 | Flash Flood | Marengo | $10,000 | A hog farm north of Marengo suffered a severe flash flood. The flood waters washed away and destroyed a hog building with about 100 hogs inside it. Over the next few days, all but 7 of the hogs were recovered alive. Residents described wading into chest-high water in an attempt to save the animals before they were swept away. |
| May 2004 | Thunderstorm Wind | Marengo | $8,000 | Semi blown over with power out. |
| April 2006 | Hail | Marengo | $5,000 | no account filed |
| March 2025 | Thunderstorm Wind | Marengo | - | Measured by wind equipement. |
| May 2023 | Thunderstorm Wind | Marengo | - | Estimated 60 mph winds from thunderstorm. |
| May 2023 | Thunderstorm Wind | Marengo | - | Estimated winds of 60 mph and higher. |
| May 2018 | Hail | Marengo | - | A trained spotter reported hail estimated to be size of between nickels and up to quarters in size. This was a delayed report. |
| September 2018 | Flood | Marengo | - | Episodes of heavy rainfall of about 5 to 15 inches in a 10 day period in much of northeast Iowa and southwest Wisconsin caused the Iowa River to rise above major flood stage at Marengo. The extended duration between the forecast and actual lower end major river flooding occurrence allowed preparations to preclude major damage downstream. Marengo rose above major flood stage of 18.5 feet at 345 PM CST on 5 September. Then crested around 19.14 feet at 630 feet at 630 AM CST on 6 September and then fell below 18.5 feet at approximately 715 AM CST on 7 September. |
| September 2018 | Flash Flood | Marengo | - | A stream gage on Big Bear Creek (LADI4) south of Ladora rose above flood stage at 430 AM and continues to rise rapidly. |
| October 2018 | Flood | Marengo | - | The Iowa River at Margeno rose above the major flood stage of 18.5 feet during the early morning hours of the 10th and fell back below the major flood stage during the evening of the 11th. The river crested at 18.8 feet around 230 PM on the 10th. |
| May 2017 | Thunderstorm Wind | Marengo | - | A trained spotter reported a large tree was down. This report was relayed from Des Moines Weather Forecast Office. |
| March 2017 | Thunderstorm Wind | Marengo | - | Measurement was relayed from a trained spotter. |
| June 2017 | Thunderstorm Wind | Marengo | - | Wind gusts were estimated to be 60 to 65 mph on the gust front of the storm, and this downed multiple trees in town. One tree fell onto power lines causing the pole to snap. Time estimated from radar data. |
| August 2016 | Flash Flood | Marengo | - | A trained spotter reported that water was 16 inches deep on roads in town. There was water that was 18 inches deep blocking a road 1.5 miles north of town. |
| June 2015 | Flash Flood | Marengo | - | Spotters observed flash flooding in Marengo, with water over 12 inches deep flowing over the road in two locations where creeks intersect the road. A spotter, located 4 miles north of Marengo, reported 4.3 inches of rain through 1140 pm. |
| November 2015 | Thunderstorm Wind | Marengo | - | A NWS storm survey team reported a roof was ripped off a metal building and a grain leg from a grain bin was ripped off. |
| June 2014 | Thunderstorm Wind | Marengo | - | A trained spotter reported 60 mph brought limbs down. |
| June 2014 | Thunderstorm Wind | Marengo | - | A trained spotter estimated winds of 60 to 70 mph. |
| April 2014 | Thunderstorm Wind | Marengo | - | A trained spotter estimated winds gusts to be 60 to 70 mph with small branches coming down. |
| May 2013 | Flash Flood | Marengo | - | Flooding was reported over Highway 6 through Marengo and just to the east. |
| June 2013 | Hail | Marengo | - | A trained spotter reported pea to penny sized hail. |
| June 2013 | Flood | Marengo | - | Heavy rain that fell late in May caused the Iowa River at Marengo to be above major flood stage of 18.5 feet to start the month. The river did not fall below major flood stage at Marengo until the early morning hours on the 4th. |
| May 2013 | Flood | Marengo | - | Heavy rains across the region during the last week of May led to a rapid rise on the Iowa River near Marengo. The river rose to and above major flood stage of 18.5 feet during midday on the 27th and then fell below major flood stage to 18.23 feet in the early morning hours on the 28th. Later that evening the river rose back above major flood stage and stayed that way through the end of the month. |
| June 2012 | Thunderstorm Wind | Marengo | - | Wind gusts estimated to be 90 mph were observed at the Iowa County Sheriff Office in Marengo, IA at 516 pm CDT June 29. |
| August 2012 | Thunderstorm Wind | Marengo | - | Emergency Manager reported multiple trees down in town. |
| April 2011 | Hail | Marengo | - | Quarter sized hail fell 1 mile south of Marengo, IA at 617 pm CDT April 3. |
| June 2009 | Hail | Marengo | - | Quarter-sized hail fell in Marengo, IA around 800 pm June 21. |
| April 2008 | Heavy Rain | Marengo | - | Rainfall of 2.50 inches flooded farm fields. |
| April 2008 | Flash Flood | Marengo | - | Heavy rain flooded farm fields south of Marengo, and streams were running bankfull. A spotter measured rainfall of 2.50 inches. |
| March 2008 | Hail | Marengo | - | A trained spotter reported nickel size hail 2 miles north of Marengo. |
| March 2007 | Thunderstorm Wind | Marengo | - | Spotter reported estimated 50 to 60 mph gusts. |
| March 2007 | Hail | Marengo | - | A spotter reported hail the size of nickels. |
| June 2007 | Flash Flood | Marengo | - | Street flooding was reported in Marengo. |
| June 2006 | Hail | Marengo | - | pea to penny size hail with heavy rain. |
| August 2004 | Heavy Rain | Marengo | - | 3 to 4 inches of rain from Marengo to Amana |
| October 2004 | Hail | Marengo | - | Cherry sized hail reported by Co-op |
| May 2001 | Hail | Marengo | - | Quarter sized hail reported by law enforcement. |
| June 1999 | Flash Flood | Marengo | - | Slow moving thunderstorms brought torrential rains of 4 to 5 inches. Numerous roads were covered in standing water over a foot deep. Several cars were washed off roads. |
| June 1999 | Flash Flood | Marengo | - | Several roads were covered in standing water. |
| June 1999 | Flash Flood | Marengo | - | Slow moving thunderstorms dumped over 2 inches of rain. Several streets were covered in standing water of around a foot. Two cars were washed into a ditch by the flood waters. |
| May 2023 | Hail | Marengo | - | no account filed |
| May 2023 | Hail | Marengo | - | no account filed |
| May 2023 | Hail | Marengo | - | no account filed |
| June 2018 | Hail | Marengo | - | no account filed |
| May 2017 | Thunderstorm Wind | Marengo | - | no account filed |
| April 2011 | Hail | Marengo | - | no account filed |
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