The wait is finally over: El Niño has officially begun.

On Thursday, the National Oceanic and Atmospheric Administration declared that the semiannual climate phenomenon has arrived. Congratulations if you took the pre-July 1 prediction on Kalshi.

Prediction markets aren’t the only places with a lot riding on El Niño. The phenomenon—characterized by hotter-than-normal waters in the eastern tropical Pacific—has a huge impact on weather in nearly every corner of the globe. And with this year’s iteration projected to be among the strongest ever recorded, the impacts are likely to be particularly acute.

There are a handful of ways to measure El Niño, but NOAA’s threshold hinges on temperatures being 1 degree Fahrenheit (0.5 C) above average for a three-month period in a specific part of the Pacific. (That area is dubbed NINO3.4 if you want to impress and/or bore someone at a party.) The Pacific surpassed that threshold thanks to a rapid upswing in temperatures in record weeks. But there are other signs of El Niño, including a surge in sea levels of up to 7 inches (18 centimeters) in the eastern tropical Pacific, thanks to winds blowing from the west that cause water to pile up there.

The shift in ocean temperatures in turn influences the atmosphere regionally, which then has knock-on effects on weather around the globe, from increasing the odds of wet weather in the southwestern US to lowering the odds of an active Atlantic hurricane season. Drought also becomes more likely in places like Indonesia and the Sahel region of Africa. El Niño also releases extra heat into the atmosphere, warming the already-heating planet even further. In essence, El Niño is like the engine of a car: Fire it up and the atmosphere gets moving.

The key questions now are how strong this year’s edition of El Niño will be and how that will affect its impacts. The answers appear to be “very” and “quite a bit.” NOAA gives this year’s El Niño a 63 percent chance of exceeding the 3.6-degree F threshold, which would qualify it as a super El Niño. But climate models are bullish that it could surpass that threshold by a wide margin. Some have it surpassing 5.4 F, which would make this the strongest El Niño on record.

There have been four other El Niños that have reached the super threshold, and all led to widespread problems around the globe. To revisit the car analogy, if your average El Niño is like the engine in a Toyota Prius, a super El Niño is more akin to the one in a Ferrari Luce.

The 1982-83 event—the first one in recorded history—caused Lake Mead to overflow, while the 1997-98 version caused what was Indonesia’s worst drought on record. The most recent iteration in 2023-24 caused Southern Africa's worst drought in 100 years, leading to 61 million people requiring food assistance. All the heat in the ocean also fries coral reefs, which are already struggling to adapt to the rising temperatures caused by burning fossil fuels.

And really, that’s the other issue at play with what will happen with this year’s El Niño. The world has never been hotter in human history. Pile an El Niño on and it’s likely there will be a burst of warming in the pipeline for this year and next. If I was a betting person, I would definitely take the over on 2026 being among the hottest years on record.