In June this year, Lake Superior experienced some interesting tidal-like water movements that received media attention on both sides of the border, describing tides, seiches, and a type of tsunami wave called meteotsunami. Here’s some background on what was happening in the lake.
For starters, tides on Lake Superior have a no-but-yes answer. Freshwater bodies of water (like Lake Superior and the Great Lakes) are considered by scientists to be non-tidal because of their smaller size compared to the wide-open expanse of oceans, so that’s a “no” answer for tides. But there’s a “yes” part. According to the National Oceanic and Atmospheric Administration (NOAA), “true tides”—which are changes in water level caused by celestial gravitational pull of the moon and sun—do occur twice daily on Lake Superior, but they are so minuscule (usually less than 2 inches) that the lakes are designated non-tidal.
However, water levels on Lake Superior can be significantly altered by a phenomenon known as seiche and meteotsunami (meteorological tsunami), which can produce tidal-like waves triggered by weather factors like severe storms, strong winds, and quick changes in atmospheric pressure. This past June, these waves on Lake Superior produced a massive seiche, which scientists are now studying to determine whether it was actually a meteotsunami.
So, what is a seiche (pronounced “saysh”)? The short definition by NOAA is that “a seiche is a standing wave oscillating in a body of water.” The back-and-forth sloshing results in the rise and fall of water levels—akin to sloshing of water back and forth (oscillating) in a bathtub or coffee in a mug. A seiche can last hours or even days, creating strong currents, and can happen in any enclosed or partially enclosed body of water. NOAA also explains: “Seiches are typically caused when strong winds and rapid changes in atmospheric pressure push the water from one end of a body of water to the other. When the wind stops, the water rebounds to the other side of the enclosed area. The water then continues to oscillate back and forth for hours or even days.”
Along the lake’s shoreline near Thunder Bay, summer camp owners Barbara and Ron Yurkoski were surprised by how long the seiche lasted. “Ron was trying to put in the camp’s water system,” said Barbara, “but the waves kept going out and then rushing back in. We’ve seen seiches a few times over the years, but this time it just kept on going.”
Tsunami on Lake Superior? While traditional tsunamis are created by seafloor events like earthquakes, a type of tsunami wave called meteotsunami can occur on Lake Superior during fast-moving weather systems such as severe thunderstorms—though it can also happen from strong winds and quick atmospheric changes. While seiches have travelling standing waves, a meteotsunami has progressive waves that travel through the water, starting at one end of the lake and ending at the other. Seiches are not rare, but a meteotsunami occurs on Lake Superior only a couple of times in a decade.
Was it a seiche or meteotsunami on Lake Superior that began overnight Friday, June 20, and ended Sunday, June 22?
A CBC News article (June 26, 2025) by reporter Michelle Allan, titled “Scientists studying suspected Lake Superior meteotsunami that left residents ‘in awe,’” quotes Eric Anderson, a scientist, associate professor, and meteotsunami researcher from the Colorado School of Mines, saying: “We have enough evidence to say that this was a meteotsunami-like event.” He also noted that it was a huge amount of water change on Lake Superior. “This is a big one,” he said.
The Duluth News Tribune reported that water-level gauges during the event recorded a change of nearly 4 feet (1.2 metres) in Ashland, Wisc.; 1.5 feet (0.5 metres) in Duluth; and up to 3 feet (0.9 metres) elsewhere along the lake, depending on where the gauge was located.
Looking back, some major seiche/meteotsunami events on the Great Lakes include:
• Lake Erie, 1844: A 22-foot seiche (6.7 metres) breached a 14-foot-high (4.3 metres) seawall, killing 78 people (NOAA).
• Chequamegon Bay, Wisc., July 11, 1935: A seiche caused a 5-foot (1.5 metres) wall of water that endangered swimmers and flooded U.S. Highway 13.
• Lake Michigan, 1954: A 10-foot-high wave (3 metres) on Lake Michigan caused a deadly surge on the Chicago shoreline that took the lives of eight people. Originally called a seiche, it has since been renamed a meteotsunami.
• Lake Superior, July 13, 1995: A large seiche on Lake Superior caused water levels to fall and rise again by 3 feet (1 metre) within 15 to 20 minutes, leaving some docked boats hanging on their mooring lines when the water retreated. Across the lake, fluctuations were reported in Rossport, Ontario; Ashland, Wisc.; and Marquette and Point Iroquois, Mich.
• Near Sault Ste. Marie, Mich., Sept. 4, 2014: A seiche was triggered by thunderstorms. The U.S. Army Corps of Engineers reported a 65-inch (1.7 metres) change in water levels. Water returned to normal within 90 minutes.
• Two Harbors, 1998: A seiche caused hundreds of thousands of dollars in damage to vessels loading at the Duluth-Missabe Iron Range Railway dock.
