Denver weather: La Niña is over. Here’s what it means for this summer.

ENSO is short for El Niño Southern Oscillation. It refers to the temperatures of the ocean water in the Pacific Ocean from South America all the way across toward Indonesia. Tracking the temperatures of the water in this area of the ocean is very important because whether that water is cooler or warmer than normal has proven repercussions of weather around the globe.

For the United States, most impacts from ENSO come during the wintertime when the winter jet stream can be influenced by the temperatures of the central Pacific. In the summertime, the most notable weather that is influenced by either ENSO condition comes during hurricane season as hurricane development is either enhanced or suppressed depending on if we are in a La Niña phase or an El Niño phase. But what do these phases mean for Colorado? Well, thanks to weather data becoming more and more available, we can see subtle but noticeable trends in our weather here from season to season.

La Niña has been in place since summer 2020 and was partly to blame for Colorado’s dry summer and dry start to winter. As La Niña has slowly weakened over the last few months, forecast models have been hinting that ENSO Neutral (near normal water temperatures in the Central Pacific) would form. And they have. La Niña is officially over and ENSO Neutral conditions are here to stay — at least through the end of summer. By fall and winter, La Niña conditions are forecast to return. According to, La Niña or El Niño conditions last for 2-7 years so this little blip of Neutral conditions is exactly that, a short blip that is expected to last through the summer months.

Regardless, an ENSO Neutral pattern in the Central Pacific will still impact global weather and those impacts to Colorado may not be exactly what we are hoping for.

Ben Castellani, a meteorologist with BoulderCast, said that La Niña taking a short summer vacation is a good thing since La Niña tends to suppress the monsoon season to the south of us while El Niño helps to amplify the reach of the monsoon thunderstorms during the summer months of June, July and August.

According to Castellani, there are only 6 occurrences in the last 50 years when an ENSO Neutral summer followed a La Niña winter. The most recent summers to feature this type of pattern were in 2018 and 2012. Both of those years featured very dry and very warm conditions across much of Colorado but that does not mean that this is our forecast. Since we are sandwiched between two prominent weather agitators, first we need to understand how these two ENSO phases impact Colorado during the summer.

What typically occurs during a La Niña summer in Colorado:

Temperatures during the summer when La Niña is present usually run higher than normal across Colorado. Since La Niña tends to suppress the monsoon season to the south, temperatures have an easier time reaching higher levels thanks to higher pressure and an overall lack of clouds. With that said, a lack of clouds means a lack of rain, and based on other years where La Niña was present, there has been a notable lack of summer moisture across northeast Colorado during this phase.

What typically occurs during an El Niño summer in Colorado:

Precipitation during an El Niño summer increases rather noticeably. The most recent El Niño summer that you may remember was back in 2015 when a moderately strong event unfolded leading to a very wet July, August and September in Colorado. It has become known that our monsoon season (which runs loosely from July through September) is positively impacted by warmer waters in the Central Pacific. Castellani said the trend is evident when you compare a La Niña summer, which tends to be drier and warmer, to an El Niño summer, which tends to be wetter and cooler. But that still leaves us with the question: What does an ENSO Neutral summer look like for Denver and the surrounding areas?

What typically occurs during an ENSO Neutral summer in Colorado:

As stated earlier, we are shifting from a La Niña winter and spring to an ENSO Neutral phase.

“Based on six occurrences of this type of ENSO shift in the last 50 years, the outlook is not as favorable for Colorado. A strong warm and dry signal is indicated across the entire state,” Castellani said. The small number of instances where we have had ENSO Neutral conditions during June, July and August have all shown that drier and warmer conditions exist in our area but, looking at a silver lining here, the amount of dryness and heat may not be as pronounced as they could be if this were a full-fledged La Niña summer.

Castellani warns that “ENSO is a global indicator that just gives us hints about conditions that are slightly more likely to occur. The “randomness” of Earth’s complicated weather patterns from year to year is much more dominant on our weather than ENSO could ever be!”

So as we continue through the summer months, yes it will get hot, and yes it will probably rain a few times — nothing too groundbreaking there but a more exciting aspect of this upcoming summer is that we will have more data to work with for the next time we find ourselves in a position where La Niña is ending and ENSO Neutral conditions are starting further expanding our understanding of global weather events and their local impacts to our area.

The Climate Prediction Center issues weekly, monthly and annual weather predictions that are regularly updated and the forecast for the upcoming summer months of June, July and August show that Colorado can expect warmer than normal temperatures and below-normal precipitation which lines up with what has previously occurred in this scenario. Time will tell but we can rest easy knowing that we are entering a potentially dry and warm period with no drought. Unfortunately, the same can’t be said for areas in Western Colorado that are bracing for a severely dry and hot summer.

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