Newcomer's Handbook Portland

Weather and Natural Disasters

By now, you’ve probably heard a few not especially funny jokes about Oregon rain. One old saw holds that Oregonians don’t tan—they rust. Another states that Portland’s rainy season only runs from September 1 to August 31. Yet another asks, “What do you call two consecutive days of rain in Portland?” (Answer: the weekend.) Then there’s the story about the hapless fellow waiting to be admitted into hell. He watches anxiously as Satan throws almost every soul in line ahead of him into the fiery pit, but notices that every so often the devil chucks someone off to the side instead. Intrigued, he summons up the courage to peep, “Excuse me, Prince of Darkness, but I notice that you seem to be throwing some people off to the side instead of into the inferno.” “Oh, them,” the devil replies ruefully. “They’re from Portland. They’re too wet to burn.” Har har har. Endless rain. How very droll.

It does rain a lot in Oregon. Rumors of a nine-month deluge, however, are greatly exaggerated. The sun comes out sometimes, even in winter, and summers are typically glorious. And even if the weather’s often wet and gray, it’s somewhat comforting that the region’s best known climatic feature is its drizzle rather than, say, category 5 hurricanes, killer tornadoes, or paralyzing blizzards.

Which is not to say that Portland is not at risk from natural disasters. All that rain sometimes begets mudslides and floods, and the area is subject to earthquakes, volcanic eruptions, forest fires, and the occasional ironic drought. It’s all part of the price you pay for living in a paradise—a soggy, geologically unstable paradise.

Weather and Climate

According to the Portland office of the National Weather Service (wrh.noaa.gov/pqr/), Portland enjoys or endures, depending on your point of view, on average, about 36 inches of precipitation per year (at the official reporting station at Portland International Airport—downtown Portland tends to be slightly wetter). Portland’s total annual rainfall is less than that of most cities in the Northeast and Southeast—Miami’s average rainfall is more than 50% higher. The difference, of course, lies in the number of rainy days. Portland’s precipitation rarely comes in the form of brief cloudbursts; rather, like the quality of mercy in The Merchant of Venice, it droppeth as the gentle rain from heaven upon the place beneath. Stated more bluntly and less elegantly, it falls over long, gray weeks of intermittent drizzle and light rain, resulting in an average of more than 150 days per year with measurable precipitation. Here’s the bad news in statistical form, showing 30-year normals, courtesy of the National Weather Service:

Month Normal Precipitation (in Inches) Mean Number of Days with Precipitation (.01 inch or more)
Yearly Total 36.03 155
January 4.88 18
February 3.66 15
March 3.68 18
April 2.73 16
May 2.47 14
June 1.7 9
July 0.65 4
August 0.67 4
September 1.47 7
October 3.00 13
November 5.63 19
December 5.49 19

You’ll notice that more than 90% of the city’s total rainfall falls from September to May. While the uneven distribution of rainfall during the year does mean the winter months are that much soggier, it also means that summers tend to be dry—newcomers who arrive during July and August are often shocked to find the city a patchwork of brown lawns. So when the pitter-patter of rain on your windows for the umpteenth day in a row threatens to drive you to suicide (or to the sunny environs of Las Vegas, which for some people amounts to the same thing), think hopefully of the blue skies and warm days of July.

While you may struggle to believe it in November and December, Portland is actually one of the drier locations in northwest Oregon. (Even within the city limits, rainfall amounts vary dramatically, and the official observation station at the airport often receives less rain than downtown Portland, and substantially less rain than the highest elevations in the West Hills.) Frequent moisture-laden storms off the Pacific Ocean drop 60 to 80 inches of rain each year on most coastal communities, and when the storm clouds hit the Coast Range and begin to rise and condense, the rain really begins to pour down. Some locations high in the Coast Range average nearly 180 inches of rain each year—that’s five times as much as Portland gets! By the time a storm reaches the Willamette Valley and the Portland area, much of the moisture has already been wrung out of the clouds. (This “rain-shadow” effect is why Portland tends to get gray skies and drizzle rather than constant downpours.) Then, when the storm hits the Cascade foothills and the clouds once again begin to rise, cool, and condense, precipitation amounts rise correspondingly. The high Cascades get more than 100 inches of “rain-equivalent” precipitation, but at that elevation it mostly falls as hundreds of inches of snow. By the time the storm passes to the east side of the mountains, there is usually very little moisture left, which is why much of central and eastern Oregon is high desert.

Despite its proximity to the Cascade Mountains and its northerly latitude—more than 45 degrees north latitude, about the same as Minneapolis and Montreal—Portland is not a snowy city. That is not to say that heavy snowfall never occurs. December 2008 was exceptionally snowy, with 19 inches of the white stuff recorded at the airport; some parts of the metro area got more than three feet of snow, and the city was essentially shut down for several days. The winter of 2013–14 was bookended by two significant snowstorms, one of which prompted the city of Portland to send out an emergency message asking residents to stay home. Such wintry events are quite rare, however. The Portland Airport averages only about 6 inches of snow per year, and in some winters there’s no snow at all on the valley floor. Elevations over 500 feet, including much of the West Hills, often get more snow than downtown Portland or the East Side (or get snow when those places do not), but even at higher elevations a heavy snowfall is rare in the metropolitan area. Near the Gorge and in the Cascade foothills, snow is much more common, although even there it is not a regular occurrence.

You may notice that extended forecasts seem to call for snow far more often than snow actually falls. According to local weatherman Matt Zaffino, “It comes down to basic climatology and geography, and Portland snow storms have to buck both to really have a chance.” Moisture usually comes from the west, out of the relatively warm North Pacific, while cold Arctic air from the North American interior has to get past the natural barriers of the Rockies and the Cascades. Often, during the winter, a computer model will predict that everything is coming together perfectly to produce several inches of snow, but ultimately either the moisture or the cold air fails to arrive. Explains Zaffino, “everything has to fall into place just right, and against the natural tendency of our weather patterns, to produce a big Willamette Valley snow storm.” The relative scarcity of snow means that anything more than a dusting of snow results in school closures and massive traffic disruptions. If you’re from a snowy part of the world, you’ll probably find this behavior amusing, frustrating, or both.

Although snow is rare, ice storms do occur with some frequency, particularly in East Portland, Gresham, Troutdale, Camas, and other communities near the western end of the Columbia River Gorge. Cold air rushing through the Gorge from eastern Oregon sets the stage for ice storms by creating a layer of sub-freezing air at ground level, with warmer air at altitude. When a storm moves in from the west, precipitation begins to fall as rain, but the rain turns to ice while falling (or freezes on contact with the ground). While ice storms can be treacherous, the effects are usually short-lived (although every few years heavy ice accumulations bring down branches all around eastern Multnomah County).

The same maritime influence that brings frequent precipitation to Portland also gives the city relatively mild temperatures. Here are the average high and low temperatures for each month, again courtesy of your friends at the National Weather Service:

Month Normal High Normal Low
January 47 35.8
February 51.3 36.3
March 56.7 39.6
April 61.4 43.1
May 68 48.6
June 73.5 53.6
July 80.6 57.8
August 81.1 58
September 75.8 53.1
October 63.8 46
November 52.8 40.5
December 45.6 35.2

The hottest temperature ever recorded in Portland was 107; the lowest was –3. In an average year, however, the mercury may hit 100 on one or two days in summer, and fall to the mid-teens on the coldest winter nights. In general, summer days are not terribly muggy; a 95-degree day in Portland may be more comfortable than an 85-degree day in Atlanta. Still, the city is subject to occasional extremes (or what Portlanders consider extremes), particularly when continental airmasses infiltrate western Oregon, and the weather can deviate significantly, in either direction, from the region’s normal climatic averages. For example, the summer of 2009 brought more 90-degree-plus days (24) than any other on record, including two consecutive days with a high of 106 degrees at Portland International Airport; just a few months later, December 2009 featured a period of record-breaking cold. Similarly, 2014 featured the coldest February on record, immediately followed by one of the warmest springs.

As a result of its complex topography, the Portland metropolitan area has many microclimates. The West Hills receive more rain than the surrounding lowlands (and create a miniature rain-shadow for downtown Portland), while Cascade foothill towns like Sandy and Estacada average more than 55 inches of rain each year. Downtown Portland and the densely populated East Side demonstrate a heat island effect; forested areas outside the heart of the city are noticeably cooler on hot days and cool down more rapidly on clear nights. Areas near the Columbia River tend to be breezy, and therefore cooler in the summer; the eastern part of the metropolitan area, near the mouth of the Columbia River Gorge, is subject to fierce winds whipping down the Gorge from the interior in the winter. The lesson here is to choose your location carefully if you have strong preferences about weather. For detailed information about Oregon weather and climate, including fun facts about record-shattering events, visit the website of the Oregon Climate Service, ocs.oregonstate.edu.

Air Pollution

Portland is not an especially smoggy city, and most of the region’s air quality problems are seasonal. On hot, still summer days, emissions from cars and industry, together with emissions from other sources (such as boat and lawnmower engines, and even paint fumes), react with oxygen to create ground-level ozone or smog. To help combat the problem, vehicle emission tests are required in the Portland metropolitan region, including Clark County, Washington. (See the Getting Settled chapter for testing requirements and locations.) For the most part, however, Portland meets national standards for clean air.

Air toxics are a more insidious problem. For example, in winter, particles associated with smoke from wood stoves and fireplaces can build up in the air and cause health problems, and particulate pollution from burning diesel fuel can be a problem at any time of year. The new cleaner-burning diesel fuel and more-efficient diesel engines required by the EPA should help decrease particulate pollution over the next few years.

The Oregon Department of Environmental Quality’s Air Quality Division (503-229-5696, oregon.gov/DEQ/AQ/) is charged with enforcing federal, state, and local air quality laws. The DEQ provides current air quality reports for various locations in and around Portland on its website (deq.state.or.us/aqi/index.aspx). The department offers the following tips for improving air quality:

  • Drive less.
  • If you use a woodstove, use an efficient, EPA-certified model, and dry firewood at least six to twelve months before burning it.
  • During hot weather, refuel your vehicle during cooler evening hours, and make sure your gas cap seals properly.
  • Wait until temperatures decrease and breezes pick up before you mow the lawn or use gasoline-powered garden equipment.
  • Consider using non-gasoline powered equipment, like a manual push mower or electric mower instead of a gasoline-powered lawn mower.

Natural Disasters

Natural disasters happen. The City of Portland has put together cheerful online maps showing your relative danger of being swept away in a landslide, scorched by wildfire, or pulverized in an earthquake; just visit Portland Maps (portlandmaps.com), type in any address or intersection, click on “Maps,” then click “Hazard.” A similar mapping feature is available for most of the Oregon portion of the metropolitan area at hazardmap.oregonmetro.gov.

Mudslides

Mudslides are one of the most common natural disasters in northwest Oregon. (According to the Oregon Department of Geology and Mineral Industries, 9,500 landslides occurred in the state during the exceptionally soggy period from February 1996 through January 1997.) The same steep hills that offer residents spectacular views also render their homes and roads vulnerable to mudslides during extended periods of heavy rain. While they are certainly not an everyday occurrence, mudslides happen often enough to warrant concern if you live (or are considering living) on or near a steep slope. The 2014 Oso landslide in Washington state, which killed dozens of people, is a reminder of how devastating a landslide can be.

Geologists warn that steep bluffs and hillsides where earth movement has occurred in the past or where geology favors such movement are most at risk. Such conditions exist in large swaths of the West Hills and other hilly parts of the metropolitan area. If you are considering buying a home in a potentially slide-prone area, you might want to consult with a geologist or geotechnical engineer to analyze the property in question. Be aware that most homeowner’s policies will not cover damage or destruction to your home caused by a landslide. Separate (usually expensive) landslide policies are available, but even these policies might not cover damage in all circumstances (e.g., if human actions contributed to the slide). If you live in a potentially slide-prone area, check with your insurer, and read the fine print carefully.

Wildfires

Western Oregon occasionally experiences drought conditions, which in turn set the stage for dangerous wildfires. While large fires are more prevalent in the drier eastern half of the state, forested neighborhoods in the Portland area, including close-in neighborhoods in the West Hills, are theoretically at risk from wildfires. The National Fire Protection Association offers tips on protecting your home from wildfire on its web site, firewise.org.

Earthquakes and Tsunamis

Oregonians live in a geologically unstable region. Earthquakes measuring at least 5 on the Richter scale hit northwest Oregon in 1962, 1964, and 1993—the last of these, centered near Salem, damaged the state Capitol building—and the Nisqually Earthquake that struck the Puget Sound region in 2001, which had a magnitude of 6.8 and caused an estimated $2 billion in damage, reminded Portlanders that bigger quakes are by no means impossible in the Northwest. Several faults run right through the metropolitan area, including one that runs directly under downtown Portland, and a large temblor on any of those faults could potentially cause significant damage and loss of life. More troubling, geologists advise us that it is only a matter of when, not if, the “Big One”—a megathrust quake of a magnitude of 9 or more—occurs along the Cascadia subduction zone 90 miles or so off the Oregon coast. The last time that happened, on January 26, 1700, some coastal areas dropped several feet in elevation, and the resulting tsunami waves pummeled the Northwest coast and even caused serious damage as far away as Japan. A similar quake today would cripple the infrastructure of the Northwest west of the Cascades, and could cause tens of thousands of deaths from Northern California to British Columbia.

For more light bedtime reading about earthquake hazards in the region, visit the website of the Pacific Northwest Seismic Network (pnsn.org), which includes data about the location and magnitude of recent (generally very small) area quakes. Also remember that earthquake coverage is not usually part of a standard homeowner’s insurance policy; be sure to look into purchasing earthquake insurance if you own, or plan to own, a home here, and consider doing a full or partial seismic retrofit.

While it isn’t really an issue in Portland proper, the entire Northwest coast is a potential tsunami danger zone. Signs in Oregon coastal communities point the way to evacuation routes; if you’re at the coast and you feel an earthquake, head inland to higher ground immediately. The threat is not merely theoretical, nor limited to Cascadia subduction zone events; the 1964 Good Friday Earthquake in Alaska generated a tsunami that struck the Oregon coast, causing significant property damage and drowning four campers on the beach at Newport.

Volcanic Eruptions

Four major, non-extinct volcanoes—Mounts Hood, St. Helens, Adams, and Rainier—are visible from downtown Portland. While three of those volcanoes are inactive (although not extinct), Mt. St. Helens, only 50 miles away, erupted spectacularly on May 18, 1980. The blast blew the top 1,300 feet off the mountain and sent a plume of ash as far east as Oklahoma. The United States Geological Survey’s Cascades Volcano Observatory in Vancouver, Washington, provides abundant information about the region’s volcanoes on its website (vulcan.wr.usgs.gov).

While Portland is far enough from all of these volcanoes that an eruption is unlikely to cause widespread destruction in the city itself, significant disruption is certainly possible. In particular, if Mount Hood were to erupt, Portland’s source of municipal water (the Bull Run reservoirs on the west side of the mountain) could become unusable.

Emergency Preparedness

The Oregon Trail Chapter of the American Red Cross offers a suite of disaster preparation tools on its website (redcross.org/or/Portland/preparedness). The Red Cross recommends taking the following steps to get ready for potential disasters:

Make a Plan

  • Research the kinds of disasters that could happen in the Northwest, and talk with your family about them.
  • Learn how to use emergency equipment, such as fire extinguishers, and know how to shut off utility service to your home. Pick two places to meet in case of an emergency, one right outside your home and one outside your neighborhood.
  • Put together a disaster kit and a stockpile of emergency supplies.
  • Make a list of emergency contact numbers and tell everyone in your household where the list is kept.
  • Practice your plan and maintain your supplies in a state of readiness.

Build a Kit

Put together a disaster supply kit with water (one gallon per person, per day) and a three-day supply of non-perishable food. The kit should include:

  • A complete first-aid kit and first-aid reference guide
  • Portable battery-operated radio and spare batteries
  • Flashlights and spare batteries
  • Blankets and extra clothing, including rain gear and sturdy shoes
  • A three-day supply of critical medication and a spare pair of eyeglasses
  • Comfort items for children, such as toys, games, stuffed animals
  • Food, water, and carrying cages and other supplies for pets
  • Plastic sheeting, duct tape, a pocket knife, matches, rope, a whistle, and other survival gear
  • A Crescent wrench, screwdrivers, a hammer, an axe, and other essential tools
  • Sanitation supplies, such as toilet paper, soap, detergent, bleach (for water purification), diapers, feminine sanitary supplies, trash bags, and pre-moistened towelettes
  • Copies of important documents and a stash of emergency cash

It may seem like a hassle to prepare so thoroughly for a disaster, given the seemingly low risk of catastrophe. However, as the Red Cross’s booklet Together We Prepare Oregon points out, “The greatest risk here in Oregon could be complacency, as many people are not aware of the potential for natural and manmade disasters in our communities. By taking these simple steps, you can help prepare your family, community, neighborhood school and workplace.”

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