San Luis Obispo experienced heavy flooding during the first week of winter quarter in January 2023. Credit: File / Mustang News

Caroline Kelleher is an anthropology and geography freshman and Mustang News Opinion Columnist. The views expressed in this piece do not necessarily reflect those of Mustang News. 

June marks the beginning of what is usually a hot California summer, which should be a welcome break from the gloom we’ve had for the first half of the year. But this year, an El Niño is predicted to wreak havoc on the West Coast, bringing intense storms reminiscent of the harsh winter we thought would be over soon.

El Niño is a complicated phenomenon, but it’s important to understand the impacts it can have on our local climate so we can be prepared for the intense storms likely to come. 

Climate: An Overview (and a SLOverview) 

Climate patterns are primarily driven by oceanic circulation. The ocean naturally works as a “conveyor belt,” mixing warm and cold water across the globe. Water near the equator is warmer because the sun is more directly overhead at the equator, so more incoming solar radiation (insolation) reaches the water and warms it. As water naturally moves to higher latitudes, it becomes colder and saltier. This makes it denser, and it sinks and begins to flow towards less dense areas of water – back towards the equator. Warm water also warms up the surrounding air, which makes it lower in pressure and rise high in the atmosphere so cold, heavier air and higher pressure rushes to take its place, causing wind.

Because SLO is so close to the ocean and land warms up faster than water, the cold ocean air moves inland to take the place of the rising warm air. This – paired with how mountainous it is – is why it’s so windy here. These factors make our temperatures fairly pleasant and consistent,  and usually only light rain in the winter, but the El Niño-Southern Oscillation (ENSO) is set to shake up these weather patterns by making it super hot and intensifying storms. We’re going to see things we usually don’t, so it’s important to learn what’s in store.

What is El Niño? 

The ENSO is a climate pattern affecting the Pacific Ocean and neighboring countries. ENSO has 3 phases: El Niño, where the water is 1-3ºC warmer in the center and east, La Niña, where the water is 1-3ºC colder in the center and east and ENSO-Neutral, where there isn’t a drastic difference. 

During El Niño, the warm water extends up further from the equator, closer to places like California. This also warms up the air, which lets it hold more water, so it creates perfect conditions for numerous powerful storms with intense rain and wind. 

An El Niño watch was just declared a few weeks ago, meaning that the El Niño conditions are very likely to develop in the coming months. In climatology, nothing can really be said to be certain — but declaring a watch of any kind basically means it’s going to happen (like a tornado watch means they’re watching a tornado). The intensity of this ENSO event will vary depending on how warm the water gets, but it’s probably going to be pretty strong. 

ENSO & the Rainy Season

How does ENSO actually affect weather that reaches us?

To answer this question, and many more, I turned to my geography professor Gregory Bohr, who has expertise in climatology (take GEOG325/Climate and Humanity, it’s soooo cool), for help. 

“During El Nino, storms and atmospheric rivers tend to track more southward into California,” Bohr said. 

He defined an atmospheric river as a “narrow plume of very humid air, a few hundred kilometers across, which blows from the ocean onto the coast.” 

These are only really problematic when they make landfall; “it’s basically like the ocean is pointing a hose at us because the humid air can hold an incredible amount of water,” Bohr said.

Could we expect to see more of these soon? Bohr said yes.

 “Warm, moist, unstable air has a better potential to create heavy rain events, so we certainly could see some big downpours and thunderstorms here in SLO during the next cold season,” Bohr said.

Sure, California is infamous for the drought we’ve withstood over the last few years — which actually ended in some counties after the storms earlier this year. But if this winter was any evidence, I really think our local infrastructure needs to be prepared for more flooding, especially on Cal Poly’s campus

The roof in my dorm has leaked many, many times over winter, and copious amounts of mold affected University Housing, which can be very dangerous. Additionally, our safety should be prioritized over academics in times of severe weather. I had a number of friends attend 8 a.m. classes in dangerous conditions before classes were canceled, even though everyone knew the rain was coming. 

When the campus remained open in March, even though the news repeatedly said conditions were too dangerous to travel in, teachers were only “encouraged” to move classes online (many didn’t), and some people even were penalized for not being able to commute to campus, which I think is ridiculous. So please, make sure your raincoat and galoshes fit, and expect to often bring an umbrella in winter. 

ENSO & Heat

While the ground might be temporarily more saturated after a severe rain event, leading landslides to be a concern, the amount of moisture in soil will undoubtedly lead to an abundance of plant growth. This was seen in the recent super-blooms, leading to both beautiful pictures and the worst allergies anyone has ever had.

Yet a tale as old as time (or maybe the last few decades) are the California wildfires. I live in the northern Bay Area, specifically in a very hilly area with lots of low shrub cover. At home, fire is a very real threat to me, my family and my friends as we’ve all evacuated before. This fear will absolutely be echoed by many in fire-prone areas in the upcoming year. 

“A wet 2023-24 winter could lead to a build up of fuel for the next fire season, having a delayed effect on future seasons,” Bohr said. 

He added that grass and low-lying brush will contribute to lower elevation fires. This is especially important because of how hot it will likely get this summer, which will increase evapotranspiration and decrease water supply to plants, causing them to wilt — which also has significant agricultural effects, especially in the Central Valley. The high snowpack in the Sierras will increase irrigation via runoff, but snowpack from just a few rainy months won’t sustain plants for as long as we need it to. 

While this summer will be noticeably warm, it’s really 2024 that we should be worried about, as it usually takes about a year for ENSO’s impact on temperature to take effect. Many buildings and pavement in cities are made of heat-absorbing material. This can cause an urban heat island effect because it’s harder to cool these structures down — especially when cities don’t have a lot of plant cover.

 With the need for more cooling in homes, I believe the increase in energy bills will push people and perhaps my own family to make the switch. For anyone in NorCal, too, I’m sure we will have to endure many planned power shut-offs or rotating blackouts to conserve energy. I would recommend keeping the blinds and windows closed all day and all night because it makes a distinct difference to the temperature inside your home. 


Climate affects us in absolutely everything we do. With the effects of climate change, our future is more unpredictable than ever. I firmly believe the meteorological media, especially on news shows, needs to present information in a more inclusive way instead of using heavily scientific terms and explanations that would require hours of Googling to understand. That way, we can understand why things are the way they are and be more prepared. 

Ultimately, there’s no definitive answer to how it will affect us in the coming years. And there isn’t even a 100% reason why ENSO and similar patterns happen and change like they do. But by just understanding a little more about our climate and climate change, we can prepare ourselves and evaluate the impacts that we have on the Earth, and vice versa.