El Niño, Spanish for 'the boy,' was named after Jesus Christ because the phenomenon resembled the weather changes observed around Christmastime.

El Niño and La Niña are Pacific Ocean climate patterns that affect global weather

El Niño causes warm water to move east, disrupting ocean life and bringing wetter conditions to the southern US and drier ones to the North. La Niña strengthens the usual wind patterns, triggering cooler northern winters and more storms in the Pacific Northwest.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

Comparing La Niña and El Niño atmosphere-ocean feedback patterns

During La Niña, trade winds reinforce the flow of warm ocean water from the eastern to the western Pacific, allowing colder subsurface water in the eastern Pacific to rise to the surface. These changes reinforce overhead air movements by altering the air temperature near the ocean surface. During El Niño, these trade winds weaken or reverse, preventing upwelling by shifting warm water back to the eastern Pacific and displacing atmospheric circulation patterns.

How El Niño and La Niña affect the Pacific and Atlantic hurricane seasons

During El Niño, trade winds push warm waters across the Pacific toward northwest South America, affecting atmospheric circulation. The resulting strengthening of vertical wind speed and direction in the Atlantic basin disrupts hurricane formation, while the weakening of this wind shear in the central and eastern Pacific basins increases hurricane likelihood. El Niña, conversely, has the opposite impacts.

Mapping how the El Niño-Southern Oscillation affects weather patterns around the world

In the warm episode (El Niño), summers in India, Indonesia, Australia, and the Caribbean are drier than normal, while winters bring wetter, cooler conditions to the US Gulf Coast and warmer conditions to the Pacific Northwest. During the cold episode (La Niña), these are reversed, with India, Indonesia, and the southern Caribbean experiencing greater rainfall in the summers.

How scientists use data to anticipate the phases of the El Niño-Southern Oscillation

Sea-surface temperatures across various regions of the equatorial Pacific Ocean can be compared with ocean temperatures elsewhere in the tropics to identify anomalies that indicate where in the ENSO cycle Earth finds itself. The "Niño 3.4" region in particular—known as the Ocean Niño Index—is a key indicator of ENSO phase and intensity.

The global impacts of the 1877 'super' El Niño and what could result from similar future events

The 1877 El Niño event lasted approximately 18 months, raised temperatures in the Niño 3.4 region of the equatorial Pacific Ocean by 2.7 degrees Celsius (4.86 degrees Fahrenheit) above average, and contributed to a global famine that killed more than 50 million people. Such events are expected to exacerbate drought-related risks to global food security, driving up food prices worldwide. (Some readers may experience a paywall.)

Understanding how the El Niño-Southern Oscillation is affected by climate change

An analysis of El Niño and La Niña patterns from 1901 to 2020 suggests that anthropogenic warming—global warming caused by humans—has at least partly contributed to increased ENSO variability in recent decades. While ENSO increases the likelihood of droughts and flooding across different regions, researchers say these severe weather events are made more extreme by greenhouse gas emissions.

How jet streams and US weather are affected by the El Niño-Southern Oscillation

Jet streams are predominantly west-to-east air currents in the atmosphere that mark the boundary between cold polar air and warm tropical air, where cells of atmospheric circulation meet. By disrupting the location of these circulations on two- to seven-year cycles, ENSO alters the probability of droughts, floods, and above- or below-average temperatures across the US.

Compare various El Niño-Southern Oscillations using maps of atmospheric and ocean variables

Because the intensity of the phases in the cycle is sensitive to small variations in atmospheric and ocean conditions and depends on complex interactions between these two systems, no two El Niño or La Niña events are identical. This contributes to the variability in the length of each phase, which is why an ENSO can last as little as two years or as long as seven.

Breaking down the health effects of the El Niño-Southern Oscillation

Second only to the seasons, ENSO is the most significant source of variability in global climate, shifting rainfall and temperature patterns, particularly in Africa, Latin America, and South and Southeast Asia. The incidence of vector-borne diseases like malaria, respiratory diseases related to wildfire smoke, food insecurity, and drought-related health and nutritional impacts has been observed to be affected by ENSO.

Learn about various ocean-atmosphere cycles impacting global weather patterns

Although the El Niño-Southern Oscillation is among the most impactful, the North Atlantic Oscillation strongly influences weather patterns in the Northeast US by periodically changing atmospheric pressure over the Atlantic. The North Pacific Oscillation fluctuates atmospheric pressure and sea-surface temperatures that affect winter temperatures over much of the US.

The top several meters of the world's oceans can hold as much thermal energy as the entire atmosphere.

Santa Claus is the result of centuries of evolving traditions

Originating from Saint Nicholas, a 4th-century bishop celebrated for his generosity, Santa's story merged with European folk legends like Sinterklaas and Father Christmas. By the 1800s, American culture redefined him, thanks to Clement Clarke Moore’s poem "'Twas the Night Before Christmas" and Thomas Nast’s illustrations.

The season celebrates Jesus' birth and anticipates the Second Coming of Christ

The Christian Bible’s New Testament features four gospels, or lives of Jesus, each of which describes the birth of Jesus in different ways (or does not mention it). Historians, both secular and religious, have sought to contextualize the biblical accounts with empirical evidence.

Christmas celebrates the anniversary of God's birth as the man Jesus

The major holiday originated in the Christian doctrine of God's incarnation in first-century Roman Judea. Though it was not celebrated for several hundred years after Jesus' death, it took on greater importance as the church spread, culminating in a global holiday season today.

Father Christmas was originally associated with decadent parties

The English figure of Father Christmas is another component of the character that would become Santa Claus. Father Christmas was depicted as eating and drinking to excess until the more austere Victorian era. He morphed into a figure dedicated to children and charity, eventually blending into the modern Santa Claus.

Saint Nicholas was a Turkish bishop from the third century

The Christian clergyman didn’t ride in a flying sleigh or have a workshop full of elves, but he was known for his generosity and anonymous good deeds, which became the basis for the story of Santa Claus.

Hear the story of Saint Nicholas, the inspiration for modern Santa Claus

A fourth-century Greek bishop in Turkey, Nicholas was known for his generosity and gift-giving. Legend holds that he secretly tossed gold bags through a window to save three sisters from slavery, which landed in stockings drying by the fire.

Christmas elves evolved from Norse mythology to Santa’s workshop

Elves originated as powerful human-sized beings in Norse mythology, closely tied to nature and fertility. In the 1800s, American writers reimagined them as tiny, toy-making assistants for Santa Claus, with later visual depictions by Norman Rockwell and Disney solidifying their role in Christmas folklore.

Dutch immigrants to America brought 'Sinterklaas,' a tradition of gift-giving to children

Dutch settlers brought Sinterklaas—their tradition of celebrating Saint Nicholas on Dec. 6 with gifts for children—to 17th-century New Amsterdam (now New York), where American culture eventually reimagined the bishop into our modern portrayal of Santa Claus.

Seven ancient ‘O Antiphons’—names for Jesus—are sung in the days before Christmas

The antiphons are prayers that express a profound longing for Jesus’ return and commemorate His birth. Each of the antiphons (for example, "O Emmanuel," the basis of the classic hymn) ascribes a different name to Jesus, like O Sapientia (“wisdom”) and O Rex Gentium (“king of the nations”).

A medieval warm period reshaped agriculture across parts of the world

Between 750 and 1350 CE, some regions experienced temperatures that rivaled or exceeded late-20th-century averages, likely due to shifts in El Niño–La Niña cycles. The warmer, wetter climate in Europe and northeast North America boosted agriculture, while causing droughts elsewhere.

The Atlantic Ocean was named after Atlas, who holds up the sky in Greek mythology, while the Pacific Ocean was named by Ferdinand Magellan.

An illustrator named Thomas Nast helped create the Santa Claus we know today

Older depictions of Saint Nicholas present a tall and thin bishop, while 19th-century illustrations from Thomas Nast gave the world Santa’s iconic white beard, big belly, jolly smile, and red suit.

Santa Claus originally wrote Christmas letters instead of receiving them

Parents originally used the letters as an opportunity to help discipline their children. Gifts eventually took on a more central role in the holiday, turning the letters into chances for kids to write Christmas wish lists.

Watch a visualization of how Earth's oceans impact its atmosphere, weather, and climate.

Track Santa and his industrious elves

Starting in December, you can follow along with Santa’s trek across the globe. Spend time on the map, play games, and even translate your holiday messages into other languages.

Advent originally had almost nothing to do with the Christmas story

Early Advent wasn’t about celebrating Jesus’s birth. In the 5th and 6th centuries, the season focused almost entirely on preparing for Christ’s Second Coming and “final judgment.” Advent’s connection to the Nativity only emerged centuries later.

Watch a visualization of global ocean currents from NASA's Estimating the Circulation and Climate of the Ocean project.

Danish folklore suggests families should treat mischievous elves to some porridge

The “nisse” is a small, demonic figure who was said to creep into barns, sometimes killing livestock. Over time, the character evolved into a friendlier Christmas elf that families could satisfy with a bowl of porridge.

Krampus is the evil counterpart to St. Nick in Alpine folklore

In Austrian and Bavarian tradition, Krampus is a horned, demonic figure who punishes naughty children with switches and chains. He is celebrated with parades and costumes around the holiday season.

Leaving cookies for Santa became popular in America during the Great Depression.

The Southern Ocean features the Antarctic Circumpolar Current—the largest ocean current on Earth—which encircles Antarctica and creates a unique biogeographical zone.

The solstice has been celebrated globally for millennia.

Krampus is known in Central Europe as Santa's scary counterpart

If you live in Austria or Germany, you've likely heard of the Krampus—a horned, half-goat demon who punishes bad children, sometimes by kidnapping them, sometimes by hitting them with birch switches, and occasionally by bringing them back with him to Hell.

Surface ocean currents are primarily driven by wind, tides, and Earth's rotation, while deep-ocean currents are driven by differences in temperature and salt concentration.

Early texts claim Jesus was conceived on the same date of his death

Though celebrations of Jesus’ birth weren’t formalized for several hundred years after he lived, it was more common to commemorate his death. Some early Church writers connected the presumed date of his death—March 25—with his conception, implying a birth date of Dec. 25.

Two Americans solidified the modern conception of Santa Claus in the 1800s

Clement Clarke Moore’s 1823 poem, now known as “The Night Before Christmas,” envisioned Santa riding a sleigh pulled by reindeer, making nighttime visits to provide gifts. Thomas Nast’s Harper’s Weekly illustrations in the 1860s–1880s established his distinctive appearance—large, bearded, and clad in an (often) red suit.

Trade winds blow from east to west due to the Coriolis Effect

Warm air rises near the equator while cooler air sinks near the poles, creating circulation patterns that curve due to Earth's rotation. At the equator, doldrums—calm regions of no wind—build warm, moist air, creating storms.

Why parts of the Earth are colder when the planet is closer to the Sun

The Earth orbits the Sun in an elliptical shape, and winter in the Northern Hemisphere occurs when the Earth reaches the point in its orbit closest to the Sun, known as perihelion. The lower temperatures result from the hemisphere tilting away from the Sun.

See Christmas traditions from around the world

From Venezuelans roller-skating to church to the decoration of boats in Greece, Christmas traditions vary widely all around the world. See examples from 30 different countries, which highlight how a country’s history shapes its holiday traditions.

Visualizing changes in ocean temperatures between 2016 and 2020

How much does the temperature of the sea change in a given year? This visualization helps illustrate the changes by showing sea surface temperature data from January 2016 through March 2020. Sea surface temperature, which refers to water temperature at the sea's surface, plays a significant role in climate and weather.

Mall Santas became a widespread tradition beginning in the 1900s

Santa Claus and commercialism are inextricable. In the early 1900s, department stores started putting “live” Santa Claus displays in their windows to help sell goods.

See what people around the world eat for Christmas

Christmas meals vary widely around the world: the British serve roast turkey and Christmas pudding, many Italians celebrate with seafood-only feasts, Filipinos eat whole spit-roasted pigs, and Mexican families enjoy tamales.

The weather time machine

A fun interactive on how old ships’ logs are giving scientists new insights into the past and future of the Earth’s changing climate (w/maps and pictures).

Saturnalia was a Roman festival that helped shape Christmas

Ancient Romans celebrated Saturnalia in mid-December, honoring Saturn, the god of agriculture, with week-long street festivals. These celebrations featured gift exchanges, lavish meals, and gambling, which was prohibited in public at the time.

Meteorological v. astronomical seasons, explained

Meteorologists and climatologists define seasons differently from “regular” or astronomical spring, summer, fall, and winter. Traditional seasons reflect the movement of celestial objects, known as the astronomical seasons; meteorologists mark seasonal change based on temperature averages.

Why Christians eat fish on Fridays during Lent

The rule isn't actually to eat fish—it's to abstain from eating warm-blooded animals on Fridays, the day of the crucifixion. Fish filled the gap because it was cheap, plentiful, and theologically convenient. As it happens, the medieval Catholic calendar's proliferation of meatless days became one of the drivers of the global fishing industry.

How salt, sunlight, and wind drive ocean currents

The Atlantic Meridional Overturning Circulation plays a critical role in regulating earth's climate, but is threatened by climate change. Explore the effects of temperature, density, and salinity on ocean currents in this 13-minute PBS video.