Publish date:

Weekend storm in Minnesota classified as rare 'mega-rain' event

It's happened just 17 times since 1973.

Stock image

The long-duration rain storm that caused flash flooding in south-central Minnesota last weekend has been classified as a relatively rare "mega-rain" event. 

The dubious classification comes from the Minnesota State Climatology Office, which explains that a large thunderstorm developed Saturday evening over Sibley County and essentially crawled to the east while back-building to the west, resulting in torrential rainfall for hours. 

"The expansive, regenerating, and long-lasting intense thunderstorms activity resulted in a wide swath of very high precipitation totals. Automated rain gauges and human observers in six different counties reported rainfall totals of six inches or greater," the Climate Journal explains. 

While radar estimates indicate some areas received around 10 inches of rain, the highest official recording submitted to the National Weather Service was 8.65 inches just south of Mankato.  

More from the Climate Journal explaining how automated rain gauges are known to underestimate rain totals by up to 10% because they can't keep up with intense rainfall rates. 

"According to radar estimates, rainfall totals closer to 10 inches may have hit an area with no observations, from southeastern Renville into southwestern Sibley County. The State Climatology Office is working with local observer networks to try to understand the extent and intensity of rainfall in this area."

Because the storm dropped six inches of rain or more over an area of "roughly 1,000 square miles," it qualifies as a "mega-rain" event. 

Here are the radar replays from the storm system. 

Radar loop from around 6 p.m. Saturday to just before midnight. 

Radar loop from around 6 p.m. Saturday to just before midnight. 

Radar loop from approximately 2 a.m to 8:30 a.m. Sunday. 

Radar loop from approximately 2 a.m to 8:30 a.m. Sunday. 

There have been 17 mega-rains in Minnesota since 1973, according to data from the Climate Office. Three were in the 1970s, two in the '80s, one in the '90s, six in the 2000s and five since 2010. 

Next Up

railroad crossing, train crossing

Woman found dead on train tracks in Moorhead

The woman was located by officials on train tracks near Memorial Park Sunday morning.

police tape, crime scene

Search for killer after man is fatally shot in Hopkins

The shooting was reported around 7:40 p.m. Sunday.

skylar hunter and jamie hunter

Victims in double killing ID'd as father and son; suspect was son's roommate

A man killed his roommate and his roommate's father early Saturday in St. Louis County, authorities said.

Mike Zimmer

‘Fire Zimmer’ trending after Vikings beat Panthers

The Vikings won the game but their coach is still on the hot seat.

Screen Shot 2021-10-17 at 8.24.33 PM

NCHC condemns Huskies fans for throwing projectiles after controversial no-call

The National Collegiate Hockey Conference says that it will be reviewing both the no-call and the aftermath.

Kirk Cousins

Kirk Cousins saves the day again to get Vikings to .500

Cousins' overtime toss to K.J. Osborn earned a 34-28 victory.

Nurses on strike

Nurses start 3-day strike at Allina WestHealth in Plymouth

A "last attempt" at negotiations failed to produce an agreement last Wednesday.

boating minnesota lake

Minnesota has experienced its deadliest boating season since 2005

Minnesota has seen 17 boating-related deaths so far this year.

Drew Doughty

Kirill Kaprizov makes Kings’ Doughty eat his words

The Kings defenseman isn't a fan of the Wild star's new deal.

Quinn Olson / UMD Hockey

Watch: UMD's Olson goes between-the-legs to set up highlight goal

Another Saturday. Another highlight for a Minnesota college hockey team.


Minnesota is getting wetter, mega-rain events increasing

We've had 11 mega-rain events since 1973, eight of them since 2000.

flash flooding

Ahead of Hurricane Laura, 'Predecessor Rain Event' could impact MN, WI

Known as a "PRE," these events happen ahead of a tropical cyclone's track.

flash flooding

Another round of torrential rain, storms possible Monday night

The heaviest rains could fall in east-central Minnesota.


Flash flooding as storms dump on Minnesota, Wisconsin

Ridiculous rainfall totals have washed out roads in western Wisconsin.

Waves of storms expected in the Twin Cities through Thursday

Waves of strong storms and heavy rain are likely Wednesday and Thursday.

storm, shelf cloud

Minnesota could be under the gun for big storms, heavy rain on Wednesday

A slight risk for severe storms may be increased to a higher probability in due time.

lightning, thunderstorm

Multiple chances for strong storms, heavy rain this weekend

Best chances are late Friday night and again on Sunday night.


Rain, storms on tap for much of Minnesota this weekend

Southern Minnesota, including the Twin Cities, could see severe weather Saturday.