How La Niña and El Niño can affect weather in Texas
El Niño, the warming of tropical waters in the eastern Pacific that has brought wetter and cooler weather to Texas, appears to be losing its influence in the atmosphere. Forecasters think it will weaken more in the spring, and they give its counterpart, La Niña, a 55% chance of returning this summer.
Texas summers are always brutal, but if La Niña — which tends to produce warmer and drier weather for us — persists strongly over fall and winter, like it did from 2020 to 2022, we could see summerlike heat linger into October, abovenormal warmth in winter and little to no rain relief at the end of the year.
What is La Niña exactly?
Don’t think of El Niño and La Niña, which are naturally occurring climate patterns, as storms or weather events that affect a specific area at a specific time. Instead, meteorologists say you should think of them as much broader phenomena, like the way road construction in one part of town can have ripple effects on traffic across a whole city.
Because the world’s oceans make up nearly three-quarters of the Earth’s surface, it shouldn’t be surprising to know that temperature shifts in the Pacific — the world’s largest ocean — can have an outsize influence on the planet’s weather.
For La Niña to develop, for instance, sea surface temperatures off the Pacific coast of South America along the equator become cooler than normal, which then significantly alters tropical rainfall and disrupts atmospheric circulation patterns. The ripple effects end up redirecting the paths of mid-latitude jet streams. These circulating rivers of air not only steer storms across the United States but also keep cold air penned up north.
When La Niña is strong, it tends to push the jet stream farther north away from Texas. As a result, polar air remains corralled up north and unable to encounter tropical air from the Gulf of Mexico. We typically depend on that confrontation of cold and warm air over Texas to produce storms and beneficial rain across the state.
What does La Niña mean for Texas?
The way La Niña tends to redirect the jet stream away from Texas can result in major shifts in temperature and rainfall for Texas and other parts of the world. Like El Niño, La Niña’s influence is strongest during the winter, from December to February, which can be critical months for Texas to replenish freshwater sources starved of rainfall in the summer.
Unseasonable winter warmth in Texas doesn’t necessarily mean less rain, but the high evaporation rates that come with heat can mean more drought. La Niña in winter typically leaves us warmer and drier than normal.
During La Niña winters in 2020-21, 2021-22 and 2022-23, according to National Weather Service records:
• Houston recorded its warmest December ever in 2021, . The average temperature for the month was 67.8 degrees, which is about 12 degrees warmer than normal.
• Austin also recorded its warmest December ever in 2021. Its average temperature for the month was 65.1 degrees, which is about 11 degrees warmer than normal.
• In 2021, San Antonio recorded its secondwarmest December ever, which had a monthly average temperature of 64.2 degrees — that’s about 11 degrees warmer than normal.
• In the final throes of La Niña last winter, Houston also recorded its fourth-warmest January and its sixth-warmest February in the past 25 years. January 2023’s average temperature was 57.9 degrees, or about 4 degrees warmer than normal, and February 2023’s average was 60.5 degrees, or about 3 degrees above normal.
• Last winter, Austin similarly recorded its fourth-warmest January in the past 25 years. January 2023’s average temperature was 56.6 degrees, or about 4 degrees warmer than normal.
Texas weather in 2022 was notable because that year was sandwiched between two La Niña winters.
In San Antonio, the year ended up being the city’s seventh-warmest ever (average temperature: 71.2 degrees). That same year, San Antonio logged only 0.32 inch of rain in January, and at year’s end, only 0.47 inch of rain in December.
For Austin, 2022 was the city’s eighth-warmest on record (average temperature: 71.1 degrees). Houston fared somewhat better: 2022 was that city’s 16th-warmest year (70.7 degrees).
Is La Niña coming back in 2024?
Yes, possibly as soon as this summer.
The most recent La Niña event dominated weather in the Northern Hemisphere during the winter of 2022-23. By February of last year, though, meteorologists detected pockets of warm water developing, with solid signs of El Niño then emerging by mid-march.
The current El Niño has a 79% chance of continuing to weaken over the coming weeks to a point where neither El Niño nor La Niña conditions are present. That could happen as soon as April, National Weather Service forecasters at the Climate Prediction Center have said.
However, the odds of La Niña developing in June through August have risen to 55% and increase to 77% by September.
Is La Niña good for hurricanes?
Although La Niña can strongly shape Texas winters, it lacks the same kind of influence in the summer because the jet stream is already positioned well north of Texas. But La Niña in the summer can lead to an increase in the number of hurricanes that develop, according to weather service meteorologists.
Wind shear — severe shifts in wind speed or direction that can tear apart storms — in the Atlantic Ocean tends to decrease during La Niña, making it easier for storms to form and strengthen.