Oregon’s climate can mostly be classified as mild. Two major geographic features dominate the climate in the state: the Pacific Ocean and the Cascade Range. The mountains of the Cascade Range act as a divide between the western and eastern sides of the state. Statewide, the coldest day of the year tends to be around January 1. It takes about seven months to reach the warmest day of the year, typically around August 1. Throughout most of the state, summers tend to be sunny and dry.
West of the Cascade Range, winters are relatively mild and wet, with precipitation usually falling as rain in the lower elevations. The areas’s proximity to the Pacific Ocean means that temperatures are moderated and significant moisure comes from the Ocean. Areas along the coast and in the Coast Range can receive upwards of 200 inches of rain annually, most of which falls from October to March. The Willamette Valley, home to about 70% of the state’s population, receives about 40—50 inches of precipitation annually.
East of the Cascade Range, temperature is less moderated by the Pacific Ocean. Central Oregon is kept dry year-round by the rain shadow created by the Cascade Range, though most of the light precipitation that it does receive also falls between October and March. Temperatures vary more substantially in the central and eastern side of the state. The abundance of clear and calm nights allow the temperature to drop significantly at night, but temperatures can climb to well over 100 °F in the daytime.