weather in Bellevue

 Weather in Bellevue, Washington is controlled by an unpredictable, often changeable general circulation of the atmosphere. The region is influenced by a low-pressure system that moves from west to east near or across Puget Sound. 

Consequently, weather conditions can vary dramatically throughout the year, with heavy rain and snow during winter months transitioning into wide temperature fluctuations during summer months.

The periods of precipitation and cloudiness, on average, occur during the winter months. Though Seattle lies in a designated temperate rainforest with a significantly heavy annual rainfall, the region is less rainy than areas in neighboring western Washington and Oregon to the south.

The record high temperature at Boeing Field in Seattle was 98 °F (37 °C) recorded on July 29, 2009; the record low minimum temperature was 0 °F (-18 °C) on January 31, 1950.

Rising above Puget Sound, Bellevue experiences a drying trend in the summer months. During the winter months, moisture from the ocean is forced inland by coastal low-pressure systems, resulting in cold and cloudy conditions. The average annual precipitation at Sea-Tac Airport is 27.87". 

The main cause of the cloudy days and cool weather during winter months is the abundance of ocean water vapor that has not been able to transpire into warmer clouds, leaving areas with more moisture in surrounding air masses. 

The warmest month at Sea-Tac Airport is August, with the average high temperature at 80.5°F (27°C) and an average low of 61.3°F (16°C). In contrast, the coldest month is December, with an average high of 46.3°F (8°C) and an average low of 30.2°F (-1°C).

The highest temperature ever recorded in Bellevue was 103 °F on June 29, 1960; the coldest temperature ever recorded was -2 °F on January 31, 1950.

The rainy season begins in October and lasts through May with occasional breaks in early December and mid to late February. The rainfall is a result of a large Pacific storm pattern that produces varying intensities of rainfall. These storms are intermittent; this allows for sunny days to mix in throughout the month. 

Heavy rainfall falls in early November, with over 7 inches of rain being recorded at times. This is also the highest amount of rainfall during the year and occurs during a cold snap. 

Storm systems then start to shift to a more northwesterly and this results in slightly warmer temperatures and some sunny days at the beginning of December. The rainfall lasts until late February, although rain occasionally starts before this point. Unexpected cool days are common after storms due to the fast change from warm ocean fog to dry air encounters.

Puget Sound also experiences winter storms which usually occur between late December and early February, with the most notable one occurring in early January 2004. This storm produced over 16 inches of snow in the city, making it one of the largest snowstorms to hit Bellevue. Other storms that have been more rare are hurricanes which rarely impact the area.

The hottest days annually are July and August with a high-temperature average of 82°F (28°C). The hottest temperature ever recorded in Bellevue was 103 °F on June 29, 1960. Humidity levels are low in the summer months. The coolest days occur during the winter months, with an average high of 49°F (9°C) and an average low of 28°F (-2°C).

The highest temperature ever recorded in Bellevue was 103 °F on June 29, 1960; the lowest temperature ever recorded was -2 °F on January 31, 1950.