Climate - Portland (Oregon)

The climate of Portland can be defined as oceanic with Mediterranean influences. In fact, winter is mild enough, but not as in the Mediterranean climate, and rainfall is frequent for many months a year, but summer is warm to hot and sunny, albeit with quite cool nights.
Portland is the largest city of Oregon and is located 100 km (60 mi) away from the Pacific coast, on the confluence of the Willamette and Columbia rivers, beyond which lies the city of Vancouver, in the state of Washington. We are in northwestern United States.
In winter, fog can form at night and in the early morning. On the coldest nights of the year, the temperature generally drops to -7/-8 °C (18/19 °F), but sometimes it can also drop below. In 1989, it went down to -13 °C (8.5 °F), and back in 1950, to as low as -19 °C (-2 °F). Sometimes it can snow, although heavy snowfalls are rare. On average, 11 cm (4.3 in) of snow fall per year.
In summer, there may be heat waves that last a few days. On the hottest days of the year, the temperature usually reaches 37/38 °C (99/100 °F). In 1981, it reached 41.6 °C (107 °F). At the end of June 2021, during an exceptional heat wave, the temperature reached 47 °C (116 °F).
Not far from Portland there are two volcanoes: 75 km (45 mi) to the southeast is Mount Hood, which is the highest peak in Oregon with its 3,425 meters (11,237 ft), while 75 km (45 mi) to the northeast, in the state of Washigton, we find Mount St. Helens, 2,549 meters (8,363 ft) high and famous for the 1980 eruption.
The average temperature of the coldest month (December) is of 5.3 °C (41.6 °F), that of the warmest month (August) is of 21.4 °C (70.6 °F). Here are the average temperatures.

Precipitation amounts to 940 millimeters (36.9 inches) per year: so, it is at an intermediate level. However, as in Seattle, excluding summer, there may be several consecutive days characterized by continuous drizzle. Rainfall ranges from 15 mm (0.6 in) in the driest months (July, August) to 145 mm (5.7 in) in the wettest (December). Here is the average precipitation.

On average, there are around 2,340 sunshine hours per year. The sun shines 23% of the time in December and 70% of the time in July (in Seattle, a little further north, the average goes from 20% in December to 65% in July). Here are the average sunshine hours per day.

Best Time

The best time in Portland is from mid-May to late September. The driest and sunniest period is generally from mid-June to early September, but it can sometimes get very hot, especially in July and August. You can therefore go from mid-May to mid-June and in the month of September.

Back to the climate of Oregon.

Portland - Weather by month

Based on the period 1991-2020

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In January, the weather in Portland is usually quite cold. The average temperature is of 5.5 °C (42 °F), with a minimum of 2.3 °C (36.2 °F) and a maximum of 8.6 °C (47.5 °F).
On the coldest nights of the month, the temperature usually drops to around -4 °C (25 °F). However, it dropped to -12 °C (10.4 °F) in January 2017.
On the warmest days of the month, the temperature usually reaches around 14.5 °C (58.5 °F). However, it reached 18.9 °C (66 °F) in January 2005.
Precipitation amounts to 130 mm (5.1 in), distributed over 19 days.
The day lasts on average 9 hours and 10 minutes.
There are on average 3 hours of sunshine per day. So, the sun shines 30% of the time.
The average humidity is 81%. Hence, the air is normally humid.
The average wind speed is 15 kph (9 mph).

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In February, the weather in Portland is usually quite mild. The average temperature is of 6.8 °C (44 °F), with a minimum of 2.7 °C (36.8 °F) and a maximum of 10.8 °C (51.5 °F).
On the coldest nights of the month, the temperature usually drops to around -3.5 °C (26 °F). However, it dropped to -10 °C (14 °F) in February 1996.
On the warmest days of the month, the temperature usually reaches around 15.5 °C (60 °F). However, it reached 19.4 °C (66.9 °F) in February 1991.
Precipitation amounts to 95 mm (3.7 in), distributed over 16 days.
The day lasts on average 10 hours and 25 minutes.
There are on average 4 hours of sunshine per day. So, the sun shines 40% of the time.
The average humidity is 76%. Hence, the air is normally humid.
The average wind speed is 13 kph (8 mph).

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In March, the weather in Portland is usually mild. The average temperature is of 9.0 °C (48 °F), with a minimum of 4.3 °C (39.7 °F) and a maximum of 13.8 °C (56.8 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around -1 °C (30.5 °F). However, it dropped to -3.9 °C (25 °F) in March 2019.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 21 °C (69.5 °F). However, it reached 25 °C (77 °F) in March 1994.
Precipitation amounts to 100 mm (3.9 in), distributed over 18 days.
The day lasts on average 12 hours and 0 minutes.
There are on average 6 hours of sunshine per day. So, the sun shines 51% of the time.
The average humidity is 73%. Hence, the air is normally humid.
The average wind speed is 12 kph (8 mph).

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In April, the weather in Portland is usually mild. The average temperature is of 11.6 °C (53 °F), with a minimum of 6.5 °C (43.7 °F) and a maximum of 16.7 °C (62 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 1.5 °C (35 °F). However, it dropped to -1 °C (30.2 °F) in April 1997.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 25.5 °C (78.5 °F). However, it reached 31.7 °C (89.1 °F) in April 2016.
Precipitation amounts to 75 mm (3 in), distributed over 17 days.
The day lasts on average 13 hours and 35 minutes.
There are on average 7.5 hours of sunshine per day. So, the sun shines 54% of the time.
The average humidity is 69%.
The average wind speed is 11 kph (7 mph).

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In May, the weather in Portland is usually very mild. The average temperature is of 15.2 °C (59 °F), with a minimum of 9.7 °C (49.4 °F) and a maximum of 20.7 °C (69.3 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 4.5 °C (40.5 °F). However, it dropped to 2.8 °C (37 °F) in May 1999.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 30.5 °C (87.5 °F). However, it reached 35 °C (95 °F) in May 2001.
Precipitation amounts to 65 mm (2.6 in), distributed over 13 days.
The day lasts on average 15 hours and 0 minutes. So the days are long.
There are on average 9 hours of sunshine per day. So, the sun shines 59% of the time.
The average humidity is 66%.
The average wind speed is 10 kph (7 mph).

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In June, the weather in Portland is usually very mild. The average temperature is of 17.9 °C (64 °F), with a minimum of 12.3 °C (54.1 °F) and a maximum of 23.5 °C (74.3 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 8.5 °C (47.5 °F). However, it dropped to 5.6 °C (42.1 °F) in June 1991.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 33 °C (91.5 °F). However, it reached 38.9 °C (102 °F) in June 2006.
Precipitation amounts to 40 mm (1.6 in), distributed over 9 days.
The day lasts on average 15 hours and 35 minutes. So the days are long. June 21, the summer solstice, is the longest day of the year in the Northern Hemisphere.
There are on average 9.5 hours of sunshine per day. So, the sun shines 62% of the time.
The average humidity is 64%.
The average wind speed is 11 kph (7 mph).

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In July, the weather in Portland is usually warm. The average temperature is of 21.2 °C (70 °F), with a minimum of 14.7 °C (58.5 °F) and a maximum of 27.7 °C (81.9 °F).
On the coldest nights of the month, the temperature usually drops to around 11 °C (52 °F). However, it dropped to 8.9 °C (48 °F) in July 2000.
On the warmest days of the month, the temperature usually reaches around 36 °C (96.5 °F). However, it reached 41.1 °C (106 °F) in July 2009.
Precipitation amounts to 15 mm (0.6 in), distributed over 4 days.
The day lasts on average 15 hours and 10 minutes. So the days are long.
There are on average 10.5 hours of sunshine per day. So, the sun shines 71% of the time.
The average humidity is 60%.
The average wind speed is 11 kph (7 mph).

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In August, the warmest month of the year, the weather in Portland is usually warm. The average temperature is of 21.4 °C (71 °F), with a minimum of 14.9 °C (58.9 °F) and a maximum of 27.9 °C (82.3 °F).
On the coldest nights of the month, the temperature usually drops to around 11 °C (52 °F). However, it dropped to 8.3 °C (46.9 °F) in August 1992.
On the warmest days of the month, the temperature usually reaches around 36 °C (96.5 °F). However, it reached 40.6 °C (105.1 °F) in August 2017.
Precipitation amounts to 15 mm (0.6 in), distributed over 4 days.
The day lasts on average 14 hours and 0 minutes.
There are on average 9.5 hours of sunshine per day. So, the sun shines 69% of the time.
The average humidity is 60%.
The average wind speed is 11 kph (7 mph).

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In September, the weather in Portland is usually warm. The average temperature is of 18.6 °C (65 °F), with a minimum of 12.3 °C (54.1 °F) and a maximum of 24.8 °C (76.7 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 7.5 °C (45.5 °F). However, it dropped to 3.9 °C (39 °F) in September 2019.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 33 °C (91.5 °F). However, it reached 36.7 °C (98.1 °F) in September 1998.
Precipitation amounts to 40 mm (1.6 in), distributed over 7 days.
The day lasts on average 12 hours and 30 minutes.
There are on average 8 hours of sunshine per day. So, the sun shines 63% of the time.
The average humidity is 65%.
The average wind speed is 10 kph (6 mph).

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In October, the weather in Portland is usually mild. The average temperature is of 13.1 °C (56 °F), with a minimum of 8.2 °C (46.7 °F) and a maximum of 18 °C (64.4 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 2.5 °C (36 °F). However, it dropped to -2.8 °C (27 °F) in October 1991.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 25.5 °C (78.5 °F). However, it reached 30 °C (86 °F) in October 1991.
Precipitation amounts to 85 mm (3.3 in), distributed over 14 days.
The day lasts on average 10 hours and 55 minutes.
There are on average 5 hours of sunshine per day. So, the sun shines 45% of the time.
The average humidity is 75%. Hence, the air is normally humid.
The average wind speed is 10 kph (6 mph).

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In November, the weather in Portland is usually quite mild. The average temperature is of 8.4 °C (47 °F), with a minimum of 4.8 °C (40.6 °F) and a maximum of 11.9 °C (53.5 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around -1.5 °C (29 °F). However, it dropped to -8 °C (17.6 °F) in November 2010.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 18 °C (64 °F). However, it reached 21.7 °C (71.1 °F) in November 1999.
Precipitation amounts to 140 mm (5.5 in), distributed over 18 days.
The day lasts on average 9 hours and 30 minutes.
There are on average 2.5 hours of sunshine per day. So, the sun shines 28% of the time.
The average humidity is 81%. Hence, the air is normally humid.
The average wind speed is 13 kph (8 mph).

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In December, the coldest month of the year, the weather in Portland is usually quite cold. The average temperature is of 5.3 °C (42 °F), with a minimum of 2.3 °C (36.2 °F) and a maximum of 8.3 °C (46.9 °F).
On the coldest nights of the month, the temperature usually drops to around -4 °C (25 °F). However, it dropped to -11.1 °C (12 °F) in December 2009.
On the warmest days of the month, the temperature usually reaches around 14.5 °C (58.5 °F). However, it reached 18.3 °C (64.9 °F) in December 1993.
Precipitation amounts to 145 mm (5.7 in), distributed over 19 days.
The day lasts on average 8 hours and 50 minutes. December 21, the winter solstice, is the shortest day of the year in the Northern Hemisphere.
There are on average 2 hours of sunshine per day. So, the sun shines 23% of the time.
The average humidity is 82%. Hence, the air is normally humid.
The average wind speed is 15 kph (9 mph).