Weather Trends for Portland, Yamhill Valley and Willamette Valley

Seasonal Expectations:

What's it going to be like in Portland and the Willamette Valley?

Planning a trip to Oregon? Here's some information to help you anticipate the kinds of weather conditions you may experience.

First, let's clear up the "rainy Oregon" perception. Yes, it rains a lot in Oregon ... if you're visiting during the months of November, December, January, February or March.

If you plan your trip in July, August or September, you can expect wonderful and dry days. It's impossible, of course, to predict what the weather will be like a few months from now. Looking back at past weather data, however, helps create some clear pictures.

The following charts show the average daily high and low temperatures each month for selected locations throughout the state. The charts also list the average monthly rainfall (and snowfall where appropriate). These averages where established by the Oregon Climate Service for the years 1971-2000.

Portland / Willamette Valley Temperature and Precipitation Averages
- 1971-2008
Oregon Climate Service

Temperatures are daily averages; precipitation and snowfall are monthly average inches

	Jan	Feb	Mar	April	May	June	July	Aug	Sept	Oct	Nov	De
Eugene
High Temp	46.5	50.7	55.9	60.6	66.8	73.3	81.5	81.9	76.6	64.6	52.1	45.7
Low Temp	33.0	34.9	36.7	38.9	42.7	47.0	50.8	50.8	46.7	40.5	37.2	33.3
Precip	7.65	6.35	5.80	3.66	2.66	1.53	.64	.99	1.54	3.35	8.44	8.29
Portland
High Temp	45.5	50.1	55.5	60.8	67.0	72.6	78.9	79.1	74.2	63.0	51.4	45.5
Low Temp	36.7	38.5	40.7	43.5	48.5	53.2	57.3	57.9	54.6	48.1	41.8	37.3
Precip	6.24	5.07	4.51	3.10	2.49	1.60	.76	.99	1.87	3.39	6.39	6.75
Salem
High Temp	47.0	51.2	56.3	61.1	67.5	74.0	81.5	81.9	76.6	64.5	52.4	46.4
Low Temp	33.5	34.7	36.6	38.8	43.6	48.4	52.0	52.1	47.7	41.3	37.9	33.9
Precip	5.84	5.09	4.17	2.76	2.13	1.45	.57	.68	1.43	3.03	6.39	6.46

Oregon Weather Rules of Thumb

George H. Taylor, the state climatologist with the Oregon Climate Service, provides detailed statistical information concerning Oregon weather patterns. Here are a few facts on which to gauge what kind of whether you may face.

• July is consistently the driest month throughout Oregon.

• Western Oregon receives the bulk of its annual precipitation during winter. In fact, there's measurable precipitation more than half the winter days. In summer, only 10 to 15% of the days are wet.

• Although there is some variation from north to south, the wettest months tend to be the November-March period.

• Although rain can occur during the warm season, average totals during those months are generally lower than during winter.

• East of the Cascade Mountains, the monthly rainfall averages are much more uniform. Some locations receive more rain in summer than in winter.

• Precipitation is highest near the coast and in higher elevations, and increasingly lower as you move eastward.

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