La Niña could mean another record-hot summer
A historically strong El Niño has been observed for the better part of the winter, but it already has started to weaken and is expected to continue doing so over the next several months. The shift is expected to be quick, and El Niño’s counterpart, La Niña, likely will take over as early as this summer.
That is why the Climate Prediction Center has issued a La Niña watch, which goes in effect whenever conditions are favorable for development for a La Niña in the next six months. According to the CPC, there is a 55% chance of La Niña conditions by meteorological summer, or June 1. The odds increase to nearly 80% by the time fall arrives.
So what does this mean?
It all has to do with changing ocean temperatures in the eastern Pacific Ocean near the equator. Lately, ocean temperatures have been far above average, signaling a strong El Niño. By summertime, ocean temperatures are expected to become cooler than average, signaling the start of a La Niña.
The presence of either El Niño or La Niña is known to change global weather patterns and shift the position of upperatmospheric jet streams. In the winter, La Niña usually means warmer and drier weather for Texas.
But what about the summer? Two of the most recent La Niña summers happened in 2011 and 2022. Those summers turned out to be a few of the hottest summers on record throughout Texas. But the question remains: Were the hot summers caused by La Niña?
To answer that question, we looked at historical temperature and precipitation data since 1950 to help determine whether La Niña plays any role in how hot a Texas summer will be.
Here are the results
Since 1950, as many as 19 La Niña events have occurred within meteorological summer, which is June through August. We then looked at the average temperature, which takes into account average highs and lows, during those La Niña summers.
In San Antonio, the average temperature during a La Niña summer has been 84 degrees. Surprisingly, the average temperature during non-la Niña summers has been slightly warmer, coming in at 84.3 degrees. So there’s a difference, but it’s a small difference.
Over in Houston, average temperatures during La Niña summers and non-la Niña summers are exactly the same, coming in at 83.5 degrees either way. Up north in Dallas, La Niña summers are actually slightly warmer than non-la Niña summers, but the difference is still less than a degree.
With conflicting data across the state, the presence of a La Niña appears to have really no significant effect on summertime temperatures. It’s summer in Texas, it’s going to be hot no matter what.
What about rainfall?
The data paints a similar picture when we look at the rainfall totals. In San Antonio, La Niña summers actually have produced 30% more rainfall than non-la Niña summers. While that sounds like a lot, the opposite is true in Houston, where La Niña summers have produced 22% less rainfall.
When you look at Dallas, the two sets of numbers are nearly identical. Here, La Niña summers have produced just 1% less rainfall than average. Across the state, the data is consistently inconsistent, meaning the differences cannot be attributed to the presence of La Niña.
Why is there no effect?
The reason for La Niña’s lack of influence in the summertime is quite simple. Meteorologist Keith White of the National Weather Service office in New Braunfels notes that it is “due to the positioning of the subtropical jet.” As the sun heats up the Northern Hemisphere in the summer, the jet stream is pushed northward, away from Texas.
“As a result, Texas is dominated by subtropical ridging, which contributes to our relative dryness and bouts of extreme heat,” White said, referring to systems of high atmospheric pressure we’ve come to know as heat domes.
As the jet stream moves south during the fall and winter months, La Niña does have a larger influence on the weather across Texas. Opposite of El Niño, La Niña typically brings weather that’s warmer and drier than average across Texas.