Summer is the peak season in Oregon, and during these months, hotel and car reservations are almost essential; the rest of the year, they're highly recommended, but not imperative. If you visit in one of the rainy months between October and May, expect lower hotel rates. It will also be easier to get reservations, especially on the coast. However, you will have to bring good rain gear. Whenever you go, keep in mind that you usually get better rates by reserving at least a couple of weeks in advance, whether you're booking a plane, hotel, or rental car. Summer holiday weekends are the hardest times of year to get room (and restaurant) reservations, especially on the coast. You should book months in advance for Memorial Day, Fourth of July, and Labor Day.
Though Oregon is famous for its gray skies and mild temperatures, the state is actually characterized by a diversity of climates almost unequaled in the United States. For the most part, moist winds off the Pacific Ocean keep temperatures west of the Cascade Range mild year-round. However, summers in the Willamette Valley and southern Oregon can see temperatures over 100°F (38°C), but on the coast you're likely to need a sweater or light jacket at night, even in August. The Oregon rains that are so legendary fall primarily as a light -- but almost constant -- drizzle between October and early July. Sure, there are windows of sunshine during this period, but they usually last no more than a week or so. There are also, unfortunately, occasional wet summers, so be prepared for wet weather whenever you visit. Winters usually include one or two blasts of Arctic air that bring snow and freezing weather to the Portland area (usually right around Christmas or New Year's). Expect snow in the Cascades any time during the winter, and even some Coast Range passes can get icy.
If you visit the coast, expect grayer, wetter weather than in the Portland area. It can be quite cool here in the summer and is often foggy or rainy throughout the year. In fact, when the Willamette Valley is at its hottest, in July and August, you can be sure that the coast will be fogged in. The best month for the coast is usually September, with good weather often holding on into October.
In the Cascades and eastern Oregon's Blue, Elkhorn, and Wallowa mountains, snowfall is heavy in the winter and skiing is a popular sport. Summer doesn't come until late in the year here, with snow lingering into July at higher elevations (for instance, the Timberline Lodge area at Mount Hood and the Eagle Cap Wilderness in the Wallowas). At such elevations, late July through August is the best time to see wildflowers in alpine meadows.
The region east of the Cascades is characterized by lack of rain and temperature extremes. This high desert area can be very cold in the winter, and at higher elevations it receives considerable amounts of snow. In summer the weather can be blazingly hot at lower elevations, though nights are often cool enough to require a sweater or light jacket.
If you're planning to go wine touring, avoid January and February, when many wineries are closed. Also keep in mind that many wineries are open daily during the summer months, but in spring and fall are open only on weekends.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.