Oregon's climate varies greatly from the western and eastern regions of the state. An oceanic climate

Oceanic climate

An oceanic climate, also called marine west coast climate, maritime climate, Cascadian climate and British climate for Köppen climate classification Cfb and subtropical highland for Köppen Cfb or Cwb, is a type of climate typically found along the west coasts at the middle latitudes of some of the...

 (also called "west coast marine climate") predominates in Western Oregon

Western Oregon

Western Oregon is a geographical term that is generally taken to mean the part of Oregon within 120 miles of the Oregon Coast, on the west side of the crest of the Cascade Range. The term is applied somewhat loosely however, and is sometimes taken to exclude the southwestern areas of the state,...

, and a much drier semi-arid climate prevails east of the Cascade Range

Cascade Range

The Cascade Range is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, and the notable volcanoes known as the High Cascades...

 in Eastern Oregon

Eastern Oregon

Eastern Oregon is the eastern part of the U.S. state of Oregon. It is not an officially recognized geographic entity, thus the boundaries of the region vary according to context. It is sometimes understood to include only the eight easternmost counties in the state; in other contexts, it includes...

. Major factors determining Oregon's climate include the large semi-permanent high pressure and low pressure systems of the north Pacific Ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

, the continental air masses of North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, and the Cascade mountains. Oregon's population centers, which lie mostly in the western part of the state, are generally moist and mild, while the lightly populated high deserts of Central

Central Oregon

Central Oregon is a geographic region in the U.S. state of Oregon and is traditionally considered to be made up of Deschutes, Jefferson, and Crook counties. Other definitions include larger areas, often encompassing areas to the north towards the Columbia River, eastward towards Burns, or south...

 and Eastern Oregon are much drier.

Precipitation

Precipitation

Precipitation (meteorology)

In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

 in the state varies widely: the deserts of eastern Oregon, such as the Alvord Desert

Alvord Desert

The Alvord Desert is a desert located in Harney County, in southeastern Oregon in the western United States. It is roughly southeast of Steens Mountain. The Alvord Desert is a dry lake bed and averages of rain a year. Two mountain ranges separate it from the Pacific Ocean—the Coast Range, and...

 (in the rain shadow

Rain shadow

A rain shadow is a dry area on the lee side of a mountainous area. The mountains block the passage of rain-producing weather systems, casting a "shadow" of dryness behind them. As shown by the diagram to the right, the warm moist air is "pulled" by the prevailing winds over a mountain...

 of Steens Mountain

Steens Mountain

Steens Mountain is a large fault-block mountain in the southeastern part of the U.S. state of Oregon. Located in Harney County, it stretches some and rises from an elevation of about above the Alvord Desert to its peak at...

), get as little as 200 mm (8 inches) annually, while some western coastal slopes approach 5000 mm (200 inches) annually.

Temperature range

Oregon has a wide range of temperature extremes throughout the state, varying from a low of -54°F to a high of 119°F, though these record temperatures are rarely experienced. The temperature in the Willamette Valley

Willamette Valley

The Willamette Valley is the most populated region in the state of Oregon of the United States. Located in the state's northwest, the region is surrounded by tall mountain ranges to the east, west and south and the valley's floor is broad, flat and fertile because of Ice Age conditions...

 is mild compared to the desert regions of the state, with high temperatures at or above 90°F occurring only five to fifteen times per year, and low temperatures below 30°F similarly infrequent. The hottest area of the state is the Southwest region, with Jackson County

Jackson County, Oregon

-National protected areas:* Cascade–Siskiyou National Monument* Crater Lake National Park * Klamath National Forest * Rogue River-Siskiyou National Forest * Umpqua National Forest -Demographics:...

 being the warmest place in the state during summer. This region is also where most of Oregon's solar and geothermal energy potential lies.

Monthly Normal High and Low Temperatures (°F) For Various Oregon Cities

City	Jan		Feb		Mar		Apr		May		Jun		Jul		Aug		Sep		Oct		Nov		Dec		Annual Precipitation
	hi	lo	hi	lo	hi	lo	hi	lo	hi	lo	hi	lo	hi	lo	hi	lo	hi	lo	hi	lo	hi	lo	hi	lo
Astoria Astoria, Oregon Astoria is the county seat of Clatsop County, Oregon, United States. Situated near the mouth of the Columbia River, the city was named after the American investor John Jacob Astor. His American Fur Company founded Fort Astoria at the site in 1811...	48	37	51	38	53	39	56	41	60	45	64	50	67	53	68	53	68	50	61	44	53	40	48	37	67.1 inches (1,704.3 mm)
Bend Bend, Oregon Bend is a city in and the county seat of Deschutes County, Oregon, United States, and the principal city of the Bend, Oregon Metropolitan Statistical Area. Bend is Central Oregon's largest city, and, despite its modest size, is the de facto metropolis of the region, owing to the low population...	40	23	44	25	51	27	57	30	65	36	73	41	81	46	81	46	72	39	62	32	46	28	40	23	11.7 inches (297.2 mm)
Brookings Brookings, Oregon Brookings is a city in Curry County, Oregon, United States. It was named after John E. Brookings, president of the Brookings Lumber and Box Company, which founded the city in 1908. As of the 2010 census the population was 6,336. The total population of the Brookings area is over 13,000, which...	55	42	56	42	58	42	60	44	63	47	67	50	68	52	68	53	68	51	65	48	58	45	55	41	73.4 inches (1,864.4 mm)
Burns Burns, Oregon Burns is a city in and the county seat of Harney County, Oregon, United States. As of the 2010 census the population was 2,806.-History:Burns was established in the early 1880s and incorporated upon Harney county's creation in 1889...	35	14	40	19	49	25	57	29	66	36	75	41	85	46	84	44	75	35	62	26	45	21	35	15	10.5 inches (266.7 mm)
Eugene Eugene, Oregon Eugene is the second largest city in the U.S. state of Oregon and the seat of Lane County. It is located at the south end of the Willamette Valley, at the confluence of the McKenzie and Willamette rivers, about east of the Oregon Coast.As of the 2010 U.S...	46	33	51	35	56	37	61	39	67	43	73	47	82	51	82	51	77	47	65	40	52	37	46	33	50.9 inches (1,292.9 mm)
Medford Medford, Oregon Medford is a city in Jackson County, Oregon, United States. As of the 2010 US Census, the city had a total population of 74,907 and a metropolitan area population of 207,010, making the Medford MSA the 4th largest metro area in Oregon...	47	31	54	33	58	36	64	39	72	44	81	50	90	55	90	55	84	48	70	40	53	35	45	31	21.1 inches (535.9 mm)
Pendleton Pendleton, Oregon Pendleton is a city in Umatilla County, Oregon, United States. Pendleton was named in 1868 by the county commissioners for George H. Pendleton, Democratic candidate for Vice-President in the 1864 presidential campaign. The population was 16,612 at the 2010 census...	40	27	46	31	55	35	62	40	70	46	79	52	88	58	87	57	77	50	64	41	48	34	40	28	13.9 inches (353.1 mm)
Portland Portland, Oregon Portland is a city located in the Pacific Northwest, near the confluence of the Willamette and Columbia rivers in the U.S. state of Oregon. As of the 2010 Census, it had a population of 583,776, making it the 29th most populous city in the United States...	46	37	50	39	56	41	61	44	67	49	73	53	79	57	79	58	74	55	63	48	51	42	46	37	43.1 inches (1,094.7 mm)
Salem Salem, Oregon Salem is the capital of the U.S. state of Oregon, and the county seat of Marion County. It is located in the center of the Willamette Valley alongside the Willamette River, which runs north through the city. The river forms the boundary between Marion and Polk counties, and the city neighborhood...	47	34	51	35	56	37	61	39	68	44	74	48	82	52	82	52	77	48	64	41	52	38	46	34	40 inches (1,016 mm)