Regional Climates Around the World

Imagine two third-grade students who are pen pals. Maria lives in Phoenix, Arizona. Kenji lives in Seattle, Washington. In January, Maria writes: "It was 65°F and sunny today—just like almost every winter day here! It hasn't rained in weeks." Kenji writes back: "It's 42°F and raining again. It rains here almost every day in winter. I can't even remember the last sunny day!"

Both students live in the same country, but their weather sounds completely different. And this isn't just one unusual week—Maria says Phoenix is hot and dry most of the year, while Kenji says Seattle is cool and rainy for months at a time.

How can two places in the same country have such different weather patterns year after year? What kind of information would a scientist collect to describe and compare the climates of Phoenix and Seattle?

• What do you think causes Phoenix and Seattle to have such different weather patterns?
• If you wanted to prove that Phoenix is usually hotter and drier than Seattle, what kind of information would you need to collect?
• How many years of weather data do you think a scientist would need to describe the climate of a place?

Weather and climate are related, but they are not the same thing. Weather is what the atmosphere is doing right now—today's temperature, whether it's raining, and how fast the wind is blowing. Climate is the pattern of weather in a place over a long period of time, usually 30 years or more. Scientists describe climate by combining many different types of weather information collected over many years.

Different regions on Earth have different climates. A region is a large area that shares similar features. When scientists describe a regional climate, they don't look at just one kind of data. They combine information from many sources—temperature records, rainfall measurements, descriptions of typical weather, and more. This helps them build a complete picture of what a region's climate is really like.

Obtaining, Evaluating, and Combining Information

One important thing scientists do is obtain and combine information from multiple sources. When studying climate, a scientist doesn't just walk outside and guess. They collect data from weather stations, look at records going back many years, read reports from other scientists, and study maps and charts.

What scientists do: They gather temperature and precipitation data for a region, organize it into tables and graphs, and then combine all of that information to describe the regional climate. They look for patterns like "this region is always warm" or "this region gets most of its rain in the spring."

What you can investigate: Look at the data table below. It shows average monthly temperature and precipitation for Phoenix, AZ and Seattle, WA. By studying this table, you are doing the same thing a climate scientist does—combining information to describe and compare regional climates.

When we look at the data table and bar chart together, some very clear patterns jump out. Phoenix is warmer than Seattle in every single month. In July, Phoenix averages a scorching 104°F while Seattle stays at a much milder 67°F. Even in January, Phoenix (56°F) is warmer than Seattle (42°F). By combining temperature data from multiple months, we can describe Phoenix's climate as hot and Seattle's as cool to mild.

Precipitation tells the rest of the story. Phoenix receives only about 8 inches of rain in a whole year. That's very little! Seattle receives about 37 inches—more than four times as much. We also notice that Seattle's rain falls mostly in winter months (January: 5.6 inches) and very little falls in summer (July: 0.6 inches). Phoenix gets a small amount of rain spread throughout the year.

By combining both temperature and precipitation information across all four seasons, we can write a complete climate description. We might say: "Phoenix has a hot, dry desert climate with very high summer temperatures and low rainfall all year." And we might say: "Seattle has a cool, wet marine climate with mild temperatures, rainy winters, and dry summers." Neither the temperature data alone nor the precipitation data alone would give us this full picture—we needed to combine them.

Scientists look for patterns to help them explain and predict what happens in nature. When we studied climate data for Phoenix and Seattle, we found clear patterns: Phoenix is always warmer and always drier than Seattle, month after month, year after year. These patterns are what make each region's climate predictable and describable.

The crosscutting concept of Patterns isn't just useful for studying climate. Scientists look for patterns everywhere! Let's see how patterns help in different areas of science.

Notice something important: in every example above, scientists found a pattern by combining information over time. They didn't look at just one day or one event. They collected data across many days, months, or years. That's exactly what climate scientists do—they look at long-term patterns in weather data to describe a region's climate.

Understanding regional climate is not just something scientists care about—it affects everyone's daily life. Farmers use climate information to decide which crops to plant. If a farmer in Phoenix tried to grow rice (which needs lots of water), it would fail because Phoenix's climate is too dry. But that farmer might grow cactus fruit or dates, which thrive in hot, dry climates.

Engineers and architects also use climate data when they design buildings. In Seattle, buildings need strong roofs that can handle months of heavy rain. In Phoenix, engineers focus on keeping buildings cool during extreme summer heat. They might design buildings with thick walls, small windows, or special cooling systems. Without combining climate information, these engineers wouldn't know what challenges to design for.

Even you use climate knowledge! If your family is planning a vacation, you probably check what the weather is usually like at that time of year. That's using climate information to make a decision. A trip to Phoenix in July? Pack sunscreen and shorts. A trip to Seattle in January? Pack a rain jacket and warm layers!

• What kind of roof would you need in a rainy climate versus a dry climate?
• Would you want big windows or small windows in a very hot climate? Why?
• Would you need more heating or more air conditioning in each region?
• How would the playground be different?

Engineers solve these problems by first combining climate information—temperature, precipitation, wind patterns, and more—and then designing solutions that fit the region's climate.

• Climate — The pattern of weather in a place over a long period of time (usually 30 years or more). Climate describes what weather is typically like in a region.
• Weather — The condition of the atmosphere at a specific time and place. Weather can change every day or even every hour.
• Region — A large area of land that shares similar features, such as similar climate, landforms, or plant life.
• Precipitation — Any form of water that falls from the sky to the ground, including rain, snow, sleet, and hail.
• Temperature — A measurement of how hot or cold something is. Climate scientists track average temperatures over many years.
• Pattern — Something that repeats in a regular, predictable way. Climate is a long-term pattern in weather data.
• Data — Information collected through observations and measurements. Scientists combine different kinds of data to describe climate.