Portlanders call the rains Portland mist. The mist brings us a lush green year around and an ideal climate for gardeners. The amount of rainfall in the Portland area is about 37 inches per year − the same as most US east coast cities. Whereas it can rain 2-3 inches in a hour or two in Washington, DC, or many mid-western areas, it will take days to accumulate 2-3 inches in Portland.
A total of about 40 inches of rainfall (includes rain, snow, hail, etc.) is Portland’s mean annual precipitation. We have four months of very rainy weather, four months of 50-50 rainy days, and four months of very dry weather. Here are the rain numbers:
The above illustration is Patrick Burke’s Portland with Rain. Patrick Burke Photography & Graphic Design features the following services: business portraiture, people, pets, products, photo restoration, and fine art photo illustration.
Coping with the Rain
Don’t let anyone kid you. It can get disheartening. Coping with the rain during the winter months is the challenge. Portlanders read, go to the movies, and find dry places like Eastern Oregon. It’s a good time to travel. The good news is that it is never really cold as evidenced by theAverage Temperatures chart below. Think positive. Rain is good for the complexion as your mother may have told you as a kid when you couldn’t go outside to play because of the rain. Dolly Parton put a positive twist on it, “The way I see it, if you want a rainbow, you gotta put up with the rain.” The comic strip, BC, added their dry sense of humor with the strip above. Carl Abbott, professor of Urban Studies at Portland State University has this to say about Portland weather in his book called Greater Portland: Urban Life and Landscape in the Pacific Northwest:
Lauren Kessler, writer and director of the Literary Nonfiction Program at the University of Oregon, puts a romantic twist on the rain. Lauren admits it took her a few years to appreciate a Western Oregon winter. She moved to Oregon in the late 70s. Here are Laurel’s words:
Sallie Tisdale’s article in The Oregonian on December 16, 2007 is entitled, “Our Blessed, Bountiful, Horrible Rains.” Below is a paragraph from her story:
We’ll move on with after this quote by Langston Hughes, “Let the rain kiss you. Let the rain beat upon your head with silver liquid drops. Let the rain sing you a lullaby.”
Snow in Portland
Yes, we get snow in Portland. If you read the official record from the National Weather Service, you will not get an accurate picture of what really happens about snow in Portland. The official record doesn’t tell the entire story because the National Weather Service office is in Northeast Portland and at a low elevation. It is an entirely different story at higher elevations. Snow forecasts always bring with them an “elevation” factor such as, “1-3 inches of snow is forecast for late afternoon at elevations of 500 feet and higher.” Here is a good example that occurred in late December 2003: On Monday, some parts of the West Hills got 7″, Salem got 6″ and Oregon City 5.5.” Moving toward the Coast Range, Buxton recorded 13″, while in the shadows of Mount Hood, Government Camp got 28″ and Timberline 42″. By late afternoon Wednesday, 3.7 inches of snow had fallen at the National Weather Service office in Northeast Portland. With the half-inch that fell Monday (December 29), 4.2 inches was the most snow recorded for a single month in Portland since February 1993, when 6.6 inches fell. By late Wednesday morning, the snow had turned to rain in downtown Portland but continued to pile up at higher elevations and closer to the gorge. So the official record will show 4.2 inches. But if you live in the West Hills (elevations above 500 feet), you were shoveling seven inches or more. January 1950 was a very cold month statewide, with frequent snowstorms. For the state as a whole, snow was the heaviest during this January than ever before since the beginning of weather record keeping, which began in 1890. Portland received close to two feet of snow in ten days. Portland’s all-time record low was also set in 1950 when it reached three below zero on February 2. Portland’s snowfall for December 2008 totaled 18.9 inches and December 2008 also marked the second-snowiest month in Portland’s recorded history, bested only by the record set in the Rose City in January, 1950 with 41.4 inches. During the period of 1871 to the present, Portland’s all-time records for snowfall include, at number one, the winter of 1892-93, with 60.9 inches of snow. The winter of 1949-50 came in third with a total of 44.5 inches, while the winter of 2008-09 totaled 23.6 inches. Climate scientists predict significantly less snow for us in coming years as the planet’s warming climate tilts the Northwest’s precipitation more toward rain. Snow Christmas Day The chances of snow on Christmas Day in the Portland area is about 1 in 100, according to an Associated Press report based on National Climatic Data Center records from 1988-2005. Visit the National Weather Bureau’s Web page entitled Some of the Area’s Snowstorms. It provides an overview of major storms in Oregon during the 1990s. The record: 224 inches at Timberline Lodge on Mt. Hood during January 1950.
Winter’s Pineapple Express and Then Summer
Mosaic of Microclimates Usually the weather stats are reported from the airport (northeast part of the city) and rainfall and temperature can vary from the airport to other parts of the city. On the same winter day, you can get rain, hail, and sun. Even within the same hour. The West Hills may experience a significant snowfall that brings trace amounts of snow to other areas. In the summer, traveling from the West Hills (lots of trees and wind currents in the hills) heading into Beaverton (west suburb) or across the river into east Portland, you will notice a increase in the temperature. Winter Portlanders watch the northern Pacific for their weather. The winter rain happens when low pressure builds in the Gulf of Alaska and the jet stream drops southward to sweep across the northern states. The counterclockwise swirl around the deep atmospheric low pumps moist Pacific air across Oregon from the west and southwest, driving ashore band after ban of clouds. Pineapple Express is the shorthand for especially juicy storms of warmer air that pick up moisture from as far to the southwest as Hawaii and drench the valleys and mountains. When a high pressure area builds off the coast and the jet stream moves north, we are guarantee dry weather. Summers are Grand Summers are dry and weeks go by without rain. Mild temperatures and low humidity. It is one of the best place in the USA during much of June, all of July and August, and a good share of September. June average seven days of temperatures to reach or exceed 80 degrees, July usually sees 15 days, and August averages 15. Portland also sees an average of 13 days of 90 degrees or above. The first frost is in early November, and the last frost in early April. 280 Growing Days Portland has close to 280 growing days according to Western Gardens by Sunset Publications. Visit Timber Press’gardening links to learn more about Pacific Northwest gardening.
Average Days per Month: Clear, Cloudy, and Rainy Skies
Source: Western Regional Climate Center in Reno, Nevada. The data is based on daylight hours only. A clear day denotes zero to 3/10 average sky cover. Partly cloudy is 4/10 to 7/10 tenths. Cloudy is 8/10 to 10/10 tenths. *.01 inches or more of precipitation.
Portland Weather Historical Data
NOAA (National Oceanic and Atmospheric Administration) keeps weather data for over 50 years on Portland. Here are some of the numbers:
Record Rainfall On December 12-13, 1882, Portland received 7.66 inches of rain in one 24-hour period and saw 10.75 inches in two days. Portland’s single-month rainfall record occurred in November 2006 when 11.92 inches fell. These facts were obtained from The Oregon Weather Book by George Taylor and Raymond R. Hatton, Oregon State University Press, ISBN 0-87071-467-8 except for the single-month record which happened after the book was published.
The National Weather Bureau’s Web site has a section entitled Oregon’s Top 10 Weather Events of 1900s which tracks floods, snowstorms, tornadoes, and wind storms.
In 1998, the Department of Geology at Portland State University published a report (MS Word document) documenting the extent of landslides following the 1996 flood and evaluating the causes. The greatest concentration of landslides in Portland was in the West Hills in the wind-blown loess of the Portland Hills Silt Formation. A total of 705 slides were studied in the project.
The Weather Café™ by Rufus provides uniquely informative long-range forecasts for specific patrons in the Pacific Northwest. Rufus’ forecasts have information of value, but even more, they show a sense of humor and are fun to read. It is a free service for patrons from British Columbia to northern California.
Portland Average Rainfall and Temperatures
Below you will find information about Portland rainfall and temperatures from World Climate.
According to the National Weather Service, winter precipitation in Portland falls mostly as rain, with an average of four days with measurable snow. Accumulations rarely exceed two inches and tends to melt rapidly. High temperatures for December through February average in the upper 40s, with lows in mid-30s. The 3-month period averages 14.03 inches of precipitation.
Factors Responsible for Portland’s Climate
The mountains (Coastal to the west and Cascades to the east) along with Portland’s latitude and proximity to the Pacific Ocean, determine the climate. Here are some of the factors mixed with general information that create the weather in Portland.
El Nino, La Nina, and La Nada
Sea surface temperatures in the equatorial Pacific have a huge impact on not only weather in the Pacific Northwest, but across the U.S. and even globally. Above-average sea temperatures usually lead to El Nino, which often translates into a milder and drier winter for the Pacific Northwest. Below-average temperatures, a La Nina, mean our winters will be colder and wetter than average. When neither condition predominates, meteorologists sometimes call it La Nada. Whether El Nino, La Nina or La Nada, Pacific Northwest winters usually can be counted on for periods of heavy rain, high winds and heavy mountain snows.
The winter season is characterized by mild temperatures, cloudy skies and rain. Winds are predominately either southerly with mild rainy spells, or easterly during colder dry spells. Outbreaks of cold arctic air from east of the Cascades will occasionally spill into the Portland area, bringing cold blustery east winds. If the east winds occur when the rain is falling over the metropolitan area, a shallow layer of cold air forms along the Columbia River. In and near this cold sub-freezing air, freezing rain and even snow will occur over eastern and northern Portland.
Spring is a transitional time as the weather patterns shift from winter to summer. As a result, March and April are wet and cool, while May and June turn drier. Temperatures during May and June often take a roller coaster ride, ranging predominantly in the 60s and 70s, occasionally reaching the 90s for a day or two. Even though the number of rain days decrease in May and June, there are still many cloudy days.
Summer finally arrives in middle to late June, when the temperature is finally able the reach the 80s on a daily basis. Northwesterly winds bring cool air from the Pacific Ocean down along the Columbia River. Summer can be quite warm, with the temperatures frequently reaching the middle 90s, although these warm days do not last long before the cool marine air arrives with temperatures in the 70s. Temperatures above 100 degrees are rare.
Autumn is the reverse of spring, with many warm days in September. By the middle of October, the rains are beginning to arrive. In addition, cooler temperatures arrive, with afternoon highs in the 50s and 60s. Fog begins to occur on a nightly basis during late October and November, with visibilities often under one mile. However, fog varies by location, with the difference frequently depending on the altitude.