Climate Insights for Lake Oswego

The climate in Lake Oswego is temperate. The average annual temperature is 12°C and approximately 1685mm of precipitation falls per year. October is the wettest month, receiving around 377mm of rainfall. Lake Oswego is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: August, July, June. The coldest months are December, January, February, when temperatures can drop to 0°C. Light snow can occur between January and December.

Temperatures in Lake Oswego vary considerably across the year, with a 30°C difference between the coldest and warmest months. The warmest month is August, when average highs reach 30°C and the mean temperature sits around 21°C. December is the coolest month, with minimum temperatures around 0°C and an average of 2°C. On average, daily temperatures fluctuate by about 10°C between overnight lows and afternoon highs. The sharpest temperature change occurs between November and December, with a 8°C shift in average temperatures.

Lake Oswego is a fairly wet location, receiving approximately 1685mm of precipitation annually, which averages out to around 140mm per month. The wettest month is October, averaging 377mm of rainfall. November and March also tend to see above-average precipitation. The driest month is August, with just 7mm. That's 370mm less than October, the wettest month. Rainfall is heavily concentrated in certain months, creating a distinct wet and dry season. Visitors should plan around these patterns, as the difference between peak and low months is dramatic. Light snowfall can occur between January and December, totalling around 43cm annually. December is the snowiest month with approximately 38cm.

Lake Oswego is relatively calm, with an average annual wind speed of 2km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is March, averaging 3km/h, though still comfortable for most outdoor activities. The calmest conditions occur in September, with average winds dropping to 2km/h, making it an ideal period for wind-sensitive activities. There is moderate seasonal variation in wind speed, with a 1km/h gap between the calmest and windiest months.

It is currently summer in Lake Oswego, which began on June 21, 2026. Lake Oswego is in the Northern Hemisphere, where spring begins in March, summer in June, autumn in September, and winter in December. The warmest period peaks in August at around 30°C, while the coldest stretch bottoms out in December near 0°C. Autumn is next, beginning on September 23, 2026 — 52 days from now.

The best time to visit Lake Oswego is during May, June, July, August and September, when the weather is most comfortable for travellers. During these months, average temperatures hover around 18°C with modest rainfall averaging 34mm per month. By contrast, December can be quite cold with temperatures dropping to 0°C. A light rain jacket is recommended, though showers are generally brief and shouldn't disrupt your plans.

The table below shows monthly climate averages for Lake Oswego based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Snow is measured in centimetres (cm) and reflects average monthly snowfall accumulation. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.