Meteorological v. astronomical seasons, explained

Why meteorologists say summer starts June 1

There are at least two periods called summer: astronomical and meteorological. Astronomical summer mirrors the movement of celestial bodies and begins roughly around June 20, with the summer solstice. Meteorologists designate the beginning of June as the start of summer to make tracking weather patterns from year to year easier.

Why we have different seasons

Visualize just how exactly seasons come to be with this animation of the earth in relation to the sun, and see how earth's tilt determines our seasons.

Climatologists use past data and advanced models to forecast future climate trends

Unlike meteorology, which focuses on weather forecasting over several days, climatology identifies trends in data over periods of 30 or more years. This data can go back millions of years and help refine models to forecast centuries into the future.

What's the difference between weather and climate?

A five-minute TedEd video exploring the differences between weather and climate – what they are, how we predict them, and what those predictions can tell us.

The science of springtime, 101

Dive into the basics on springtime including the astronomy that brings it about, natural signs of spring's arrival, and some of the cultural approaches to the season.

How the months of the year got named

Curious about how the months got their names? This article from The Old Farmer's Almanac explores the origins of today’s Gregorian calendar. Based on the ancient Roman lunar calendar, the months were named after Roman gods until winter when the names changed to numerical titles. Read along to learn the significance and intentions behind labeling each lunar cycle.

Asia's agriculture-focused set of 24 'small seasons'

In contrast to the four broad seasons and their basis in astronomy and climate, ancient farmers in China and Japan had many more and varied seasons (or "sekki). Take Keichitsu (March 6 to 21), for example: this means "going-out of the worms" when bugs come out from hibernation.

The difference between solstice and equinox, explained

A solstice marks the extremes in the amount of day or night, while the equinoxes come on days with a balance between the two. Learn why with this brief video.

Changes in Earth's orbital cycles influence the timing of ice ages

These cycles include changes in Earth's orbit shape, tilt, and wobble, all of which alter how much solar energy different parts of Earth receive over time. Due to orbital eccentricity, summers in the Northern Hemisphere last about 4.5 days longer than winters.

Monsoons are large, seasonal shifts in wind driven by land-sea heating differences

Because land heats and cools faster than water, pressure differences form and create significant sea breezes. Moist air pulled onto land rises, condenses, and leads to substantial summer rainfall.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

The Köppen-Geiger system divides Earth’s climate into five main categories

This classification system, developed by a German-Russian botanist and a German climatologist, results from differences in the intensity of solar radiation and rainfall in different parts of the world. Each category is further divided into multiple coded zones.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

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.

Explore every meteor shower from space

Every year, Earth travels through a series of meteor showers—the Perseids in August, the Lyrids in April—and a fraction of them light up the sky as they hit the atmosphere. Explore each group of meteors with this fascinating, year-round interactive.

The expedition produced the first detailed climate records of the West

Lewis and Clark logged daily temperature, weather, and seasonal patterns throughout their journey, creating the earliest systematic meteorological record for the western territories of the United States. Their observations helped overturn longstanding views that weather west of the Appalachians was similar to the East Coast.

Its predictability distinguishes SAD from other forms of depression

Most major depression is "stochastic"—brought on without a clear trigger. SAD—also known as major depression with a seasonal component—is unique in that its onset is predictable. Many of those affected can predict its occurrence accurately within a range of three weeks. This podcast explores this unusual feature of SAD, among other expert takes.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Environmental determinism links human traits and societal progress to geography

Also known as climatic determinism, the theory states that the latitudes where people are located influence their emotional and intellectual capabilities. Originating in Ancient Greece, these ideas were used throughout history to justify racial hierarchies.

How do scientists study far away stars?

Astronomy is the only science that is purely observational: meaning, scientists can't study stars in a lab. Here's a breakdown of how modern researchers use new tools to understand objects billions of light years away. As it turns out, the rules of science allow us to identify, categorize, and experiment with phenomena light years away.

Moon's visibility is determined by its declination, equivalent to Earth latitude

The Moon's declination varies between approximately +28.7 degrees and -28.7 degrees, ensuring it rises and sets between latitudes of approximately 61.3 degrees north and south. This means there are places on Earth where the Moon is never visible above the horizon and places where it temporarily does not set.

Seasonal allergies don't always show up in childhood

The human immune system may become sensitized to pollen and develop an allergic reaction to it after prolonged exposure. Other triggers for new seasonal allergies may include exposure to new environments and changing climate conditions that affect allergy season length and conditions for various pollens.

Chronological versus biological age

Science has come to understand different types of aging. What we call age is simply the number of years since birth, or chronological age. At the cellular level, biological aging happens at different rates for different people, and explains why some seem to age more quickly (or slowly).

Astronauts follow strict schedules to mimic Earth days and stay healthy in space

Experiencing 15 sunrises and sunsets a day while aboard the International Space Station, visitors preserve their circadian rhythms and mental health with fixed timetables. Astronauts have described sleep as living in a vacuum cleaner due to ongoing air filtration.

Early timekeeping tools included sundials, water clocks, and astrolabes

Astrolabes also provided a person's latitude based on the height of the stars in the sky, thus aiding in navigation. Incense and candle clocks relied on the constant burning rate of fire to track the passage of time based on premarked locations with equal-interval spacing.

Scientists quantify how far from the poles auroras will be visible using the G-scale

The Geomagnetic Storm scale indicates the expected severity of the deformation of Earth's magnetic field based on the amount of energy injected by the solar wind. Solar activity is monitored using various satellites to forecast these storms, which can also be used to anticipate damage and disruption to power systems, radio communications, and satellite navigation.

Understanding why the thermosphere feels cold, despite exceeding 2,000 degrees Celsius

High-energy solar radiation can raise temperatures above 2,000 degrees Celsius (3,632 degrees Fahrenheit), but the air density in this layer is so low that there would be insufficient collisions between energized molecules and a person's skin to cause them to experience this warmth. Variations in the level of solar radiation reaching the layer cause it to swell and shrink.

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.

Shooting stars, or meteors, are fragments of asteroids and comets that burn up as they enter Earth's atmosphere, creating streaks in the sky called meteor showers.

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

Hurricanes, which rely on air consistently spinning in the same direction, cannot cross the equator because air curves in opposite directions north and south of it.

Planeterrellas create artificial auroras that mimic the atmospheric displays of light by setting up an electric field between two metal balls in a jar filled with a small amount of air.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

Dirty lightning is a thunderstorm created from friction between rising and falling flows of ash and smoke during volcanic eruptions.

Poison ivy can cause rashes year-round since all parts of the plant contain urushiol, the oil that triggers our allergic response.

Some Pokémon have been named after real and fictional organisms, while some real-world species have been named after Pokémon, such as Chilicola charizard and Binburrum zapdos.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

Crows are believed to have intelligence on par with a seven-year-old child and demonstrate complex behaviors, from problem-solving with tools to recognizing human faces.

Corals are themselves not coral reefs—the term refers to the tiny marine invertebrates that build the rigid reef.

The term 'algorithm' originated from the Latinized name of al-Khwārizmī, a 9th-century mathematician whose works introduced Arabic numerals and the decimal-based numeral system to Europe and whose treatise 'Al-Jabr' gave algebra its name.

The 19th-century painters of the Hudson River School were among the first American romantics, with portraits that displayed the natural beauty of the young country.

Long before Major League Baseball began allowing instant replay for balls and strikes, an umpire reluctantly used the technology to determine whether a hit was a home run, a move that inadvertently ushered in a new era for the sport.

See photos of Meteora, a mountainous site in central Greece, home to 14th-century monasteries perched atop soaring outcroppings.

Hedge funds, the private investment firms that trade a wide swath of financial assets, make money by imposing steep fees on investors and from the fund's investment performance.

Apeirophobia is an overwhelming fear of living forever, perhaps stemming from the brain's inability to conceptualize an infinite life.

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.

Children are now three times more likely to say they want to be a YouTuber when they grow up than an astronaut, with some even attending 'YouTube camps' that teach kids how to create content for the platform.