Eastern Oklahoma, western Arkansas could face periods of above-normal rainfall if El Niño persists

By Wayne Adams, Climate Scientist

Eastern Oklahoma and western Arkansas could face an increased potential for periods of heavy rainfall during 2027 if the current El Niño remains influential into the spring. The developing climate pattern is already unusually strong. As of September 2026, NOAA’s Climate Prediction Center indicates that El Niño is strengthening, with a high probability of becoming a very strong event during fall and winter 2026–27.

There is still considerable uncertainty about how long El Niño will persist. That will be particularly important for eastern Oklahoma and western Arkansas. If El Niño remains influential through late winter and spring, changes in the storm track could favor periods of increased precipitation across portions of the southern United States.

El Niño changes atmospheric circulation across the Pacific and North America, influencing the position of the jet stream and storm systems. Historically, El Niño winters often favor wetter conditions across portions of the southern United States, although every El Niño behaves differently. A strong El Niño therefore does not guarantee excessive rainfall in eastern Oklahoma or western Arkansas.

History nevertheless demonstrates how wet this region can become when a favorable large-scale climate pattern combines with repeated storm systems. Fort Smith normally receives roughly 47 inches of precipitation annually, but rainfall reached 73.93 inches in 2015. May 2015 alone produced an extraordinary 19.85 inches at Fort Smith. National Weather Service records also show extraordinary 2015 totals elsewhere in the region, including more than 83 inches near Sallisaw and more than 84 inches near Wilburton.

Those numbers demonstrate an important point about the 2027 outlook. It isn’t necessary for 60 inches of rain to fall between January and June to create serious flooding. Several heavy-rain events occurring close together can be more important than the total rainfall over six months. Once soils become saturated, additional rainfall runs off more efficiently into creeks, rivers and reservoirs.

Wister Lake could become an important indicator

One of the most important places to monitor would be Wister Lake. The reservoir is part of the Poteau River system and was constructed partly for flood control. The Poteau River enters the eastern portion of the reservoir, while the Fourche Maline enters from the west. The U.S. Army Corps of Engineers operates the lake to provide flood protection along the Poteau River downstream toward the Arkansas River.

During an extended wet period, increasing runoff from both the Poteau River and Fourche Maline watersheds would increase inflow into Wister Lake. The reservoir can temporarily store large quantities of floodwater and allow that water to be released more gradually. However, repeated storms can progressively consume available flood-storage capacity.

The events of 2015 provide an important example. According to the U.S. Army Corps of Engineers, Wister Lake received its largest recorded monthly inflow volume in May 2015 — approximately 701,510 acre-feet, equivalent to about 13.25 inches of runoff over the drainage basin. The lake reached an elevation of 508.33 feet on May 26. Later that year, Wister experienced a record peak inflow of approximately 144,190 cubic feet per second on Dec. 28.

That doesn’t mean 2027 will repeat 2015. It demonstrates what this watershed is capable of producing when repeated heavy rainfall occurs.

Poteau River flooding

The Poteau River would also need to be watched carefully if a wet pattern persists into spring.

Heavy rainfall upstream can increase river levels before the water reaches Wister Lake. Downstream, reservoir releases combine with rainfall entering the watershed below the dam. Communities from the Wister and Poteau areas northward through Panama and toward Fort Smith can therefore experience very different river conditions depending upon where the heaviest rainfall occurs.

The December 2015 event demonstrates how extreme the Poteau River can become. During that event, the river reached approximately 31.44 feet near Poteau, while an estimated crest of 44.97 feet occurred near Panama.

Flooding doesn’t require rainfall to fall directly over Panama or Poteau. Water falling many miles upstream eventually moves through the watershed. That makes the geographic distribution of rainfall just as important as the total amount.

Fourche Maline could feed large amounts of water into Wister

The Fourche Maline watershed is another important part of the flood equation.

The Fourche Maline drains a substantial area west of Wister Lake before entering the reservoir. Heavy rainfall around the Talihina, Red Oak and surrounding areas could therefore produce increasing inflow into Wister Lake even if rainfall immediately around Wister were considerably lighter.

This creates the possibility of different parts of the watershed contributing runoff simultaneously. If both the Poteau River and Fourche Maline basins receive repeated heavy rainfall, Wister Lake could receive significant inflows from both sides of its drainage system.

Arkansas River adds another factor

The final part of the system is the Arkansas River.

The Poteau River eventually joins the Arkansas River near Fort Smith. During widespread regional flooding, the Arkansas River itself can already be running extremely high when water arrives from the Poteau watershed.

That can create backwater flooding along the lower Poteau River. Instead of water moving freely downstream, a high Arkansas River can contribute to elevated water levels farther back into the Poteau system.

This occurred during the December 2015 flood. Major flooding along the Arkansas River contributed to backwater flooding along the Poteau River in northern LeFlore County. Roads became impassable, agricultural areas flooded, a Panama-area water-treatment facility was surrounded by water, and an apartment complex was evacuated.

That interaction makes the Arkansas River especially important. Flood conditions in LeFlore County cannot always be understood simply by looking at how much rain falls locally.

January through June could be the critical period

If the El Niño pattern persists, January through June 2027 could become an important period to monitor.

The scenario that would cause the most concern would be a sequence rather than one individual storm: winter rainfall increases soil moisture, rivers and reservoirs remain elevated, additional storms arrive during March and April, and then the normally active spring storm season produces repeated heavy rainfall during May and June.

Under those circumstances, even moderate storms later in the season could produce greater runoff because the ground would have less capacity to absorb additional water.

This is why rainfall totals alone don’t tell the entire story. Thirty to 35 inches distributed evenly across six months would have a very different impact than the same amount falling during several concentrated periods.

The timing and location of rainfall would determine whether Wister Lake and the surrounding river systems simply run high or experience significant flooding.

What history tells us

Historical strong El Niño events also provide an important warning against assuming that every strong event will be exceptionally wet.

Some strong El Niño years around Fort Smith have produced relatively modest precipitation, while others have been much wetter. The extraordinary rainfall of 2015 demonstrates the upper end of what can happen locally, but it should not be treated as the expected outcome for 2027.

For that reason, predicting a specific annual rainfall total this far in advance would carry considerable uncertainty. A range of outcomes remains possible.

What can reasonably be said is that if a strong El Niño persists and a wetter southern storm track becomes established, the potential for repeated heavy-rainfall events across eastern Oklahoma and western Arkansas deserves close attention.

2027 climate outlook

The developing El Niño makes precipitation one of the important climate variables to watch going into 2027. The evolution of El Niño through winter, Gulf of Mexico moisture, soil moisture, reservoir levels and the location of the spring storm track will provide increasingly useful information as the season approaches.

For LeFlore County, four interconnected water systems deserve particular attention: Wister Lake, the Fourche Maline, the Poteau River and the Arkansas River. A prolonged wet pattern could affect all four, and conditions in one part of the watershed can influence another.

This outlook should not be interpreted as a prediction that flooding will occur. It is a long-range climate assessment of what could happen if El Niño remains strong and a wetter pattern develops.

As winter approaches and additional climate information becomes available, the potential for a wet 2027 can be reassessed. If rainfall begins accumulating early and Wister Lake, the Poteau River and surrounding watersheds enter spring unusually wet, the potential for significant flooding would become considerably more important to monitor.

---

Don’t let social media companies decide what or when you should read a post. Sign up for our free newsletter and never miss a story on local news, sports, obits and more.