Why Is the Pacific Northwest So Rainy?

iStock
iStock

The Pacific Northwest is home to some of the most breathtaking scenery in the United States, but that greenery comes at a cost. It rains in the Pacific Northwest, and it rains a lot. Despite the gorgeous landscapes and cosmopolitan cities, the western parts of Washington and Oregon get a bad rap for how gray and dismal they can be. But why exactly does it rain so much in the Pacific Northwest?

The reason gloomy weather is so common boils down to prevailing weather patterns and the unique terrain that makes this part of the world so gorgeous. This stretch of land between Portland, Oregon, and Seattle, Washington, usually finds itself directly under the track of the jet stream. The jet stream is a fast-moving river of air that encircles the Northern Hemisphere right around the latitude of the U.S.-Canadian border.

Whenever the jet stream swoops to the south, creating a trough, it can generate low-pressure systems at the surface that produce heavy rain and high winds. These troughs and resulting low-pressure systems often intensify in the Gulf of Alaska and over the Pacific Ocean off the coast of Washington, allowing large storms to crash into the coast with ease. Most of these storms are run-of-the-mill rainmakers, lasting for a day or two before moving on, but some of them can be enormous and cause significant wind damage and flooding.

While the photogenic low-pressure systems that swirl into the coast are the driving force behind the Pacific Northwest’s seemingly endless rains, it’s the region’s terrain that locks in those dismal weather conditions. When moist winds blow inland with an approaching storm, the high terrain of the Cascade Range forces the moist air to rise into the atmosphere, enhancing the thick clouds and steady rainfall.

Cloudy skies over the Pacific Northwest on May 16, 2017.SSEC/MODIS Today

Even though it rains quite a bit along the northwestern coast, actual rainfall totals in the Pacific Northwest vary wildly from place to place due to changes in elevation. Some spots at high elevation right along the coast or along the Cascade Range can see more than 10 feet of precipitation in a single year, accounting for both rain and the equivalent amount of liquid in snowfall.

Seattle, Washington, and Portland, Oregon, each only see around 36 inches of rain every year, which hardly makes these bustling metro areas the wettest in the country. Compare their rainfall totals to New York City’s Central Park, which measures nearly 50 inches of rain every year, and Mobile, Alabama, commonly one of the wettest cities in the United States; its proximity to the Gulf of Mexico gives it nearly 66 inches of rain every year.

The rain that does fall in Seattle and Portland, though, falls over a longer period of time. Between 1981 and 2010, both cities saw a little more than 150 days with measurable precipitation per year, compared to about 122 rainy days in New York City and just 115 in Mobile. This accounts for the Northwest’s reputation as the gloomiest part of the country—but makes for spectacularly green landscapes when the skies clear out.

Looking to Downsize? You Can Buy a 5-Room DIY Cabin on Amazon for Less Than $33,000

Five rooms of one's own.
Five rooms of one's own.
Allwood/Amazon

If you’ve already mastered DIY houses for birds and dogs, maybe it’s time you built one for yourself.

As Simplemost reports, there are a number of house kits that you can order on Amazon, and the Allwood Avalon Cabin Kit is one of the quaintest—and, at $32,990, most affordable—options. The 540-square-foot structure has enough space for a kitchen, a bathroom, a bedroom, and a sitting room—and there’s an additional 218-square-foot loft with the potential to be the coziest reading nook of all time.

You can opt for three larger rooms if you're willing to skip the kitchen and bathroom.Allwood/Amazon

The construction process might not be a great idea for someone who’s never picked up a hammer, but you don’t need an architectural degree to tackle it. Step-by-step instructions and all materials are included, so it’s a little like a high-level IKEA project. According to the Amazon listing, it takes two adults about a week to complete. Since the Nordic wood walls are reinforced with steel rods, the house can withstand winds up to 120 mph, and you can pay an extra $1000 to upgrade from double-glass windows and doors to triple-glass for added fortification.

Sadly, the cool ceiling lamp is not included.Allwood/Amazon

Though everything you need for the shell of the house comes in the kit, you will need to purchase whatever goes inside it: toilet, shower, sink, stove, insulation, and all other furnishings. You can also customize the blueprint to fit your own plans for the space; maybe, for example, you’re going to use the house as a small event venue, and you’d rather have two or three large, airy rooms and no kitchen or bedroom.

Intrigued? Find out more here.

[h/t Simplemost]

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links.

7 Facts About the Hurricane Highway

Hurricane Earl (top) and Hurricane Fiona (bottom) pummel the U.S. coast and Caribbean islands.
Hurricane Earl (top) and Hurricane Fiona (bottom) pummel the U.S. coast and Caribbean islands.
NOAA/NASA GOES Project // Public Domain

Autumn is the peak of hurricane season, also known as Cape Verde season, after the islands where the so-called "hurricane highway" originates. Here are seven facts about this awesome—and sometimes deadly—weather phenomenon.

1. The hurricane highway begins near the African coast.

The Cape Verde Islands, located off the northwest coast of Africa, are where the hurricane highway starts. Thunderstorms destined to become hurricanes often form into a tropical depression near the islands, slowly organizing and strengthening over the following week as the system moves toward the Caribbean. These storms have a long time to get their act together, but they also have to cover a lot of distance without losing their power to reach the East Coast as a hurricane. Some storms are able to thrive with little wind shear, ample warm water, and moist air, while others starve and dissipate if they encounter cooler waters and strong winds, or ingest dry, dusty air blowing off the Sahara Desert.

2. An easterly jet stream gives rise to the hurricane highway.

It’s hard to imagine from North America that a couple of thunderstorms on another continent thousands of miles away can swirl up into a monstrous storm, but it happens almost every year. The extreme temperature gradient between the blistering heat of the Sahara Desert and the more temperate climate of the savanna to its south creates an easterly jet stream that triggers clusters of showers and thunderstorms. These clouds then move from east to west, emerging off the western African coast near the Cape Verde Islands. Every year, the right conditions turn a handful of these localized storms into tropical storms that make their way across the Atlantic.

3. The biggest hurricanes start with the smallest storms on the hurricane highway.

Hurricane Andrew was a Category 5 hurricane when it made landfall in Homestead, Florida.Xanxz/NOAA, Wikimedia Commons // Public Domain

Hurricanes, cyclones, typhoons—these are all names for the same force of nature, like Hurricane Andrew, which hit the East Coast in 1992. Cyclones like Andrew don’t just form out of thin air. All tropical cyclones require a relatively tiny “nucleus” of thunderstorms in order to develop. When the air and water temperatures are right, these groups of thunderstorms sometimes spin up into a fierce low-pressure system capable of causing a lot of damage. We see lots of these seedling thunderstorms over the ocean every year, but only a small number of them become hurricanes.

4. Hurricanes form in different places in different months.

Where a tropical storm or hurricane begins its trip across the ocean depends on what time of the year it forms. Storms that form early in the season usually get their start from thunderstorms or cold fronts that stall over the water very close to land; almost all of the storms that form in the Atlantic in June come to life within a few hundred miles of land. When we reach the peak of hurricane season, though, they start to form farther and farther out in the ocean—all the way out to the shores of Africa.

5. Fall is the peak of hurricane season on the hurricane highway.

Hurricane season in the Atlantic Ocean runs from June 1 through November 30. Storms are most common during that six-month stretch of the year, but sometimes they can form earlier or later too. That said, the period between the middle of August and the middle of October is typically the climatological peak of the season. That’s because, as the ocean water gets warmer, the atmosphere becomes conducive to vigorous storms, increasing the risk for hurricanes and tropical storms.

6. Cape Verde hurricanes can easily land in the record books.

This image shows the tracks of all tropical cyclones recorded in the Atlantic Ocean between 1851 and 2014.
Dennis Mersereau

Tropical waves traveling west from the coast of Africa in the middle of the summer are the culprits behind some of the worst hurricanes we’ve experienced in the United States. For example, on August 8, 2005, a small tropical wave emerged off the coast of Africa, soon becoming Tropical Depression 10. That depression would fall apart a few days later, but its remnants kept moving toward the U.S., redeveloping into a new tropical depression over the Bahamas on August 23. That new tropical depression became Hurricane Katrina, the costliest hurricane to ever strike the United States.

It’s a similar story for many—but not all—major hurricanes in recent history. Hurricanes Andrew, Dennis, Ivan, Isabel, and Ike were all Cape Verde–type storms that sprang to life thousands of miles away from where they would ultimately wreak havoc.

7. Strong hurricanes can still form in other places in autumn.

While the far eastern part of the Atlantic Ocean is a hotbed of activity this time of the year, it’s not the only place you need to watch if you live near the coast. Storms that form close to land can quickly spin themselves into catastrophe. Hurricane Sandy formed just south of Jamaica and hit New Jersey in a matter of days in 2012. A tropical depression that developed east of Florida on September 18, 2005, exploded into Hurricane Rita just three days later, with 180 mph winds—the most intense storm ever recorded in the Gulf of Mexico.

Meteorologists are currently predicting an above-average hurricane season in 2020. It may be worth preparing: NOAA suggests gathering a few key disaster supplies to have on hand, getting an insurance check-up, and locating the safest high ground.