El Niño on the Horizon: Can the Warm Phase End Six Years of Drought in the Southern Plains of the U.S.?
Does El Niño Mean the Drought Across the Southern Plains Will Definitely End? No.
There is a growing possibility that an El Niño will be among the strongest influences on weather patterns across the U.S. later this year. What will this mean for drought in the Southern Plains?
El Niño is the warm phase of the El Niño-Southern Oscillation, or ENSO. El Niño usually (but not always) coincides with cooler, wetter conditions for the Southern U.S. Its influence is usually (but not always) strongest from late fall through early-to-mid spring. El Niño patterns can become drought busters for the Southern U.S., as occurred in the winters of 1957-58, 1982-83, 1997-98, and 2015-16. However, we can’t always count on an El Niño to eliminate drought, as in 1953-54, 1972-73, and 2023-24.
One Good Year Won’t Eliminate 6 Years of Water Deficit…
…unless it’s exceptionally wet, like in 1957-58. Those years also saw historic floods that led to fatalities and devastating destruction. Although they bring a lot of water, floods don’t always end a drought. Sometimes a place can experience a drought and flood at the same time. Last year, we wrote about rapid shifts from drought to flood in Texas.
So what about this drought? Why wouldn’t an El Niño end this one? It could, but it would have to bring exceptionally wet weather. The American Southwest and the Southern Plains have been in drought for nearly 6 years. As a result, reservoirs are low, streamflow is low, and aquifers are low. It will take more than one wet year to refill low reservoirs, streams, and aquifers.
Further, many large reservoirs in the Southern Plains rely on winter snowpack upstream to fill. This includes along the Rio Grande and the Pecos River in western Texas. Given the poor existing snowpack in this region, current runoff forecasts are below normal. Looking ahead to next winter, ENSO is somewhat useful for predicting snowpack in the Rio Grande headwaters to an extent, but the relationship is weak. A few examples from past years: The 2022-2023 (La Niña year) snowpack was great, but did little to improve long-term hydrologic drought. 2023-24 (El Niño year) saw above-average snowpack in the Rio Grande headwaters, while the 2024-251 snowpack was below average.
The Strength of the El Niño Matters for Drought Prediction in the Southern Plains
Generally, the stronger the sea-surface temperature anomaly, the more likely the expected atmospheric response. This means there is more confidence in forecasts for wetter fall, winter, and early spring seasons across the Southern U.S. In February, NOAA’s Climate Prediction Center shifted to using the Relative Oceanic Niño Index (RONI) to provide a better sense of the magnitude of sea-surface temperature variability in the context of overall warming oceans.
The magnitude of warming during an El Niño pattern is important. One example is the 2023-24 El Niño and seasonal weather patterns in the Southern U.S. Using the traditional Oceanic Niño Index (ONI), the 2023-24 El Niño looked like it was going to bring more precipitation with it, but the atmospheric response and follow-on effect on rainfall patterns were weaker than expected. The RONI showed a dampened El Niño signal and was more aligned with the weather patterns experienced. Looking ahead, if an El Niño develops in fall 2026, RONI should give a more accurate measure of the expected impact on weather across the Southern U.S.
Focusing in on just Texas, the table below looks at all the El Niño events since 1950, their relative strength, and the impacts to weather. For most of the mid-20th century, RONI was either close to or sometimes stronger than the traditional ONI, and the impacts on winter precipitation followed the traditional ONI fairly well. However, as the tropical oceans warmed (mostly in the early 21st century), precipitation patterns were more aligned with the RONI through Texas.
If an El Niño pattern forms in the Pacific later this year, there’s no guarantee it will remove drought conditions in the Southern Plains. Typical El Niño weather patterns would bring needed improvement to drought across the Southern Plains, but they will not definitely end it without being historically wet, which could bring other consequences (flooding).
Table 1: ONI and RONI values with impacts on drought in Texas. Here we are defining El Niño’s strength using the December-January-February traditional ONI and RONI. A weak El Niño is defined as an anomaly between +0.5-0.99 ºC, a moderate El Niño is between +1.0-1.49 ºC, strong is between 1.5-1.99 ºC and a very strong El Niño is 2 ºC or warmer.
| El Niño Period | Strength (Traditional ONI) | Strength (Relative ONI) | Texas Impacts |
|---|---|---|---|
| 1951-1952 | Weak | Weak | None. Record-setting drought continued. |
| 1953-1954 | Weak | Moderate | None. Record-setting drought continued. |
| 1957–1959 | Strong | Very Strong | Ended the catastrophic 1950s drought of record with equally catastrophic floods. |
| 1963-1964 | Moderate | Moderate | A moderate to severe drought saw significant improvement. |
| 1965-1966 | Moderate | Strong | Drought returned in the summer but improved in the winter. |
| 1968-1969 | Moderate | Moderate | Relatively average conditions persisted through winter. |
| 1972–1973 | Strong | Very Strong | Provided significant moisture after dry early 1970s. |
| 1976-1977 | Weak | Moderate | Following a 3-year La Niña pattern, winter 1976-1977 was very wet, but extreme drought returned the following summer. |
| 1977-1978 | Weak | Weak | Some drought improvement, but severe drought persisted. |
| 1982–1983 | Very Strong | Very Strong | Extremely wet winter for Louisiana and Mississippi; fairly average for Texas. This likely prevented drought development. |
| 1986-1987 | Moderate | Strong | Very wet winter, especially for western Texas and the Panhandle. |
| 1987-1988 | Weak | Weak | None. Average winter precipitation and drought returned the following spring. |
| 1991-1992 | Strong | Very Strong | Very wet winter. |
| 1994-1995 | Moderate | Moderate | Wetter-than-average winter for eastern Texas. Drier-than-average winter for western Texas. |
| 1997–1998 | Very Strong | Very Strong | Drought returned in spring 1996 but did not last long. 1997 was a persistently wet year, and the 1997-1998 winter was wetter than average. |
| 2002-2003 2004-2005 2006-2007 | Weak | Weak | The early 2000s experienced three weak El Niño events. Each El Niño winter saw above-average precipitation. The 2006-2007 winter precipitation ended an extreme but short-term drought. |
| 2009-2010 | Moderate | Moderate | Wet winter in northeast Texas; average elsewhere. |
| 2015–2016 | Very Strong | Very Strong | Ended the intense 2010–2015 Southern Plains drought, but included localized flooding. |
| 2018-2019 | Weak | Weak | Above-average winter rainfall followed by a very wet spring and summer. |
| 2023–2024 | Strong | Moderate | Provided relief, but did not eliminate the 2020–2023 drought. |
Thank you to Michelle L'Heureux (NOAA's National Weather Service Climate Prediction Center) and Andrew Hoell (NOAA's Physical Sciences Laboratory), who reviewed this story.
1. Using the Oceanic Niño Index, 2024-25 was an ENSO-neutral year, but using the Relative Oceanic Niño Index, 2024-25 was a weak La Niña. Precipitation patterns across the southwest resembled a traditional La Niña pattern. Learn more about drought and the Relative Oceanic Niño Index here.
