The United States is enormous.
At 9.82 million square kilometers, it is slightly smaller than Canada, and is the third-largest country in the world by size.
The nation shares the world’s longest border with Canada up north, and Mexico down south. It is bound by the Atlantic Ocean in the east, and the Pacific to its west.
Due to the state of Alaska, the USA also has a sea border with Russia. In fact, at some points of the map, on the Bering Strait, they are just three miles apart!
Naturally, a nation of such immense size displays a wide variety of regional climates.
The different climate zones within the United States are due to changes in latitude, and variations in topography. From the Rocky Mountains to the plains of Kansas, there are a wide diversity of physical features that in turn affect the weather.
Moreover, the Gulf Stream current, a submerged river of warm water that flows from the Caribbean to Iceland, runs parallel to the east coast, causing changes in climate.
How Many Climate Zones Are There in the Continental United States?
The regional climates of the United States can be divided into several distinct types. Let’s take a look at each.
1. Southwest
States – Arizona, Colorado, New Mexico, Texas, Utah
The southwest is marked by a hot, dry climate that has led to the formation of a desert in parts. The main cities are Phoenix and Denver. Temperatures can soar above 100°F in summer. Even at night, the temperature rarely drops below 80°F in some areas. The winters are pleasant with a high of 60°F.
From July to September, parts of the region receive a good amount of rainfall. These rains originate in the Gulf of California, and have allowed cities such as Boulder, Colorado to grow. But, droughts are frequent, and parts of New Mexico have not seen rain for several years.
It should be noted that not all of this zone is dry and hot. Due to the Rocky Mountains and other mountain ranges, areas at higher elevations tend to be much cooler in the summer, and can even see significant snowfall in the winter.
2. West
States – California and Nevada
Parts of Nevada are extremely arid. Near the border with Mexico, the rainfall is greater, and has helped Las Vegas to thrive. Summers in Nevada can be brutal in their ferocity.
The cool ocean current offshore has allowed California to be blessed with Mediterranean weather. The daily high in San Francisco during summer ranges between 62° and 68°F.
Further inland, there is a steep temperature gradient, and the valleys are much warmer. This leads to frequent outbreaks of wildfires that are increasing with climate change.
A small portion of this region is so inhospitable that it is known as Death Valley. Located in the Mojave Desert, Death Valley is below sea level, and a foreboding place of extreme temperatures. If Death Valley seems slightly familiar, it is because this was where George Lucas shot the scenes from Tatooine, the desert planet that was home to Luke Skywalker, the protagonist of Star Wars.
3. Southeast
States – Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Virginia
States adjoining the Gulf of Mexico and near the Atlantic are humid and have a subtropical feel. The summers are hot and damp. The winters are pleasant with lows of 60°F.
Cities in the interior, such as Atlanta, are somewhat drier than Tampa and New Orleans, which are located close to the coast.
The coastal states receive precipitation year-round with violent tropical storms headed in from the Atlantic. Official hurricane season stretches from June to November. The most infamous was Hurricane Katrina in 2005, which submerged New Orleans (known for Mardi Gras and jazz) for many weeks.
The constant rainfall has led to the growth of thick mangrove forests and swamps in parts of the southeast.
4. Midwest
States – Iowa, Illinois, Indiana, Kansas, Missouri, Nebraska, Ohio, Oklahoma
The central portion of the USA has a cool temperate climate.
Rainfall is fairly evenly spread throughout the year. The summers are warm, with highs seldom exceeding 90°F. The winters are chilly, with the temperature dropping to freezing soon after fall.
Wind blowing down from Canada bring winter storms.
This region is known for sudden temperature shifts as warm air from Mexico collides with cold air from the north.
This gives rise to tornados; storms that have a narrow radius, but ferocious winds that are strong enough to drive a blade of grass into soft bark. Every year they leave devastation in their wake.
Tornado alley extends throughout this region.
5. North-Central
States – Montana, North Dakota, South Dakota, Wyoming
During the summer these states have a humid climate, not unlike that in Europe.
The lows can touch 0°F or colder in winter, and highs can reach 80°F in summer. Climate change, however, has thrown these calculations out of the window.
This zone receives ample snowfall every winter. Due to the Rocky Mountains, parts of the region receive very little rainfall the rest of the year, being in the rain-shadow area. On average, June is the wettest month of the year.
6. Northeast
States – Delaware, Maine, New Jersey, New York, Pennsylvania, Maryland, Massachusetts, New Hampshire, Rhode Island, Vermont
The climate of this region varies widely. The proximity to the Atlantic, Great Lakes, and being at the edge of the temperate zone (50° latitude) means there are many factors at play.
The interior states, such as Maryland, are cold and snowy, while the coast (Massachusetts and New Jersey) is exceptionally suitable for human habitation. Due to this reason, some of the largest cities of the U.S. can be found here in relative proximity to each other.
Summers are warm, but not harsh. Winters are freezing, and snowfall happens as late as April.
7. Northwest
States – Washington, Idaho, Oregon
Most of the region has a cool and wet climate. The summers are mostly dry, but winter is wet, with regular rainfall at the end of the year.
Because it is adjacent to the Pacific, it escapes the fierce cold of the central regions. Along the intermountain plateau, weather is semi-arid and dry for most of the year.
The summer highs are pleasant. This fine weather has led to Seattle emerging as the headquarters of Amazon and Microsoft, two of the largest companies in the USA.
Climate of Alaska and Hawaii
1. Alaska
The northernmost state of the USA is bitterly cold most of the year. The warmest weather extends from June to August, with highs of 70°F.
After September, for six months, the temperature is well below freezing. Life in Alaska can be arduous for much of the year if you are not comfortable with winter temperatures.
2. Hawaii
Hawaii is a very special spot for climatologists.
The archipelago displays 10 different climatic zones! From sunny tropical weather in Honolulu, the capital, to snowfall on the summit of Mauna Loa, you can find every type of climate here.
Severe thunderstorms are common year-round. The islands are in the middle of a vast ocean, so this is natural. Cyclones are not unknown. A strange feature of Hawaiian weather is the formation of monster hailstones about four inches long and two inches wide during thunderstorms.
A Summary
To make it easy to understand, divide the U.S. into four quarters.
The states at the bottom left are dry and arid with the exception of California. Those at the bottom right are humid and hot.
In the upper section, those on the right are cold, but bearable. Those on the upper left are cold, but as one approaches the Pacific, it becomes warmer. This is of course a huge generalization. But it helps distinguish between the climate zones of the USA. Regardless of where you plan to visit or live, you would be wise to bring clothing that covers a wide variety of weather.
