Climate is the long-term pattern of weather in a specific area, typically measured over 30 years. While weather changes hour to hour, climate describes what you can generally expect from a region’s temperatures, rainfall, humidity, and wind across seasons and decades. Scientists calculate these 30-year averages, called Climate Normals, to define what’s typical for any given place on Earth.
How Climate Differs From Weather
Weather is what’s happening outside right now: today’s rain, tonight’s frost, this afternoon’s wind. Climate is the bigger picture. If you’re planning a vacation to Thailand in July, you check the weather forecast for next week, but you already know from climate data that July is hot and rainy there. That expectation comes from decades of recorded observations averaged together.
Scientists track precipitation, temperature, humidity, sunshine, and wind over long periods to build a climate profile for each region. These profiles let us compare places, predict growing seasons, design buildings, and understand how ecosystems function.
The Five Major Climate Zones
The most widely used system for classifying climates divides the world into five major groups based on temperature and precipitation patterns. Developed by climatologist Wladimir Köppen and later refined by Rudolf Geiger, this system helps explain why the Amazon feels nothing like the Sahara, and why London’s weather behaves so differently from Moscow’s.
Tropical
Tropical climates sit near the equator, where every month averages above 64°F (18°C). Temperatures typically hover between 68°F and 86°F year-round with little seasonal variation. In tropical rainforest zones, every month receives at least 60 mm of rain, feeding dense forests and some of the richest biodiversity on Earth. Tropical monsoon and savanna climates share the warmth but have distinct wet and dry seasons, with several months receiving far less rainfall.
Dry (Arid and Semi-Arid)
In dry climates, evaporation outpaces precipitation. Deserts are the most extreme version: cloudless skies create enormous temperature swings, with scorching daytime heat plunging below freezing at night. Not all deserts are hot, though. The Gobi Desert in east Asia has an annual average temperature below 0°C. Semi-arid steppes are slightly less extreme, receiving a bit more moisture but still not enough to support forests. Both hot and cold deserts force plants and animals into remarkable adaptations to survive prolonged water deficits.
Temperate
Temperate climates cover a wide middle ground. Humid subtropical zones (think the southeastern United States or parts of eastern China) have hot summers above 72°F (22°C), mild winters, and rain spread throughout the year. Marine west coast climates, found in places like the Pacific Northwest and western Europe, stay milder and more consistent, with no month averaging above 72°F and rainfall distributed evenly across the year. Mediterranean climates, like those in southern California or Greece, feature dry, hot summers and wet winters, with the wettest winter month receiving at least three times the rainfall of the driest summer month.
Continental
Continental climates exist in the interiors of large landmasses, mostly in the Northern Hemisphere. They’re defined by dramatic seasonal contrasts. Humid continental areas have hot or warm summers but severe, cold winters. Subarctic regions push this further, with cool summers and brutally cold winters. If you’ve experienced a Minnesota January followed by a sweltering July, you’ve felt a continental climate firsthand.
Polar
Polar climates are the coldest on the planet. Found at the highest latitudes and elevations, these regions have no true warm season. Ice cap climates stay below freezing year-round, while tundra climates may briefly warm just enough for surface ice to melt in summer.
What Determines a Region’s Climate
Three geographic factors do most of the work in shaping any location’s climate: latitude, elevation, and proximity to water.
Latitude is the dominant force. As you move farther from the equator, average yearly temperatures drop. Latitude also controls rainfall patterns in a predictable way. Belts of low atmospheric pressure near the equator and around 60° north and south produce heavy precipitation. Belts of high pressure centered at 30° north and south create dry conditions, which is why so many of the world’s great deserts cluster around those latitudes.
Elevation works like a second layer on top of latitude. As you climb higher, temperatures drop, roughly 3.5°F for every 1,000 feet of elevation gain. That’s why a city like Quito, Ecuador, sits right on the equator yet has spring-like temperatures year-round at over 9,000 feet above sea level.
Large bodies of water act as a thermostat. Coastal areas experience smaller temperature swings between day and night and between summer and winter, because water heats and cools much more slowly than land. Coastal regions also tend to receive more precipitation, especially on the side of the landmass that faces the water.
Why Climate Changes Over Long Timescales
Earth’s climate has never been static. Over tens of thousands to hundreds of thousands of years, slow shifts in the planet’s orbit around the Sun drive enormous climate swings, including the ice ages. These shifts, known as Milankovitch cycles, involve three overlapping patterns.
First, Earth’s orbit stretches from nearly circular to slightly elliptical and back again, changing the planet’s distance from the Sun. Second, the tilt of Earth’s axis wobbles between 22.1° and 24.5°, which intensifies or softens the seasons. A steeper tilt means hotter summers and colder winters; a shallower tilt creates milder seasons that allow snow and ice to build up at high latitudes. Third, the direction Earth’s axis points gradually rotates in a cycle averaging about 23,000 years. Together, these three cycles can vary the solar energy reaching mid-latitudes by up to 25 percent, enough to trigger or end an ice age.
Once ice starts building, it reflects more sunlight back into space, cooling the planet further in a feedback loop. When the cycles shift the other direction, warming accelerates as ice retreats and darker land or ocean absorbs more heat.
How Climate Is Measured Today
Modern climate monitoring combines ground-based weather stations with satellites. Surface stations record temperature, precipitation, humidity, and wind at thousands of locations worldwide. Satellites add a global view, measuring things that ground stations can’t easily capture: how reflective Earth’s surface is (which affects how much solar energy gets absorbed), wildfire impacts on air quality, and variations in solar energy output. By combining both data streams, scientists can track climate patterns across every continent and ocean simultaneously.
Recent Global Trends
Earth’s climate is measurably warming. As of early 2025, the global surface temperature exceeded the pre-industrial average (1850 to 1900) by 2.41°F (1.34°C). Atmospheric carbon dioxide, the primary heat-trapping gas, reached 427 parts per million in February 2025, up from around 280 ppm before the Industrial Revolution. That roughly 50 percent increase is the main driver behind rising global temperatures, shifting rainfall patterns, and more frequent extreme weather events that are gradually reshaping climate zones around the world.