Seattle’s weather is defined by its temperate maritime climate, heavily influenced by its position between the saltwater of the Puget Sound and the freshwater of Lake Washington, with two major mountain ranges—the Olympics to the west and the Cascades to the east—acting as atmospheric barriers.
Seasonal Trends
The Dry Season (July – September)
Summers in Seattle are legendary for their mild perfection. Unlike the humid heat of the East Coast or the scorching dry heat of the Southwest, Seattle summers are pleasantly warm and low in humidity.
- The Feel: Highs typically hover in the mid-70s°F (24°C). The air is crisp, and the sun sets late—often after 9:00 PM in late June.
- Phenomenon: Residents rely on the "Marine Push" (natural air conditioning), where cool ocean air rushes in at night to drop temperatures, often accompanied by a morning "marine layer" of clouds that burns off by noon.
The Wet Season & "The Big Dark" (October – March)
This is the period that earned Seattle its rainy reputation. However, it rarely pours; instead, it persistently drizzles. Locals call the stretch between November and February "The Big Dark" due to the combination of heavy cloud cover and short northern days.
- The Feel: Temps stay in the 40s°F (7°C). The rain is often a fine mist or aerosol-like drizzle that doesn't always necessitate an umbrella but creates a constant dampness.
- Historical Context: While total rainfall (approx. 39 inches) is less than cities like Miami or New York, Seattle has more rainy days (around 150 per year), leading to a prolonged "gray" sensation.
Transitional Spring (April – June)
Spring is a tug-of-war between seasons. You may experience "May Gray" and "June Gloom," where the marine layer lingers longer into the day. This is also when the cherry blossoms at the University of Washington peak, usually amidst alternating sun and light showers.
Microclimates and Regional Variations
Seattle is a city of hills and water, creating distinct weather variances over just a few miles:
- The Puget Sound Convergence Zone: This is the most famous local weather phenomenon. Air moving around the Olympic Mountains collides north of downtown (usually near Northgate or Shoreline), creating a narrow band of intense rain, hail, or even snow while the rest of the city remains dry.
- Ballard "Snow Hole": Due to its low elevation and proximity to the water, the Ballard neighborhood often sees rain while higher-elevation spots like West Seattle or Queen Anne are getting dusted with snow.
- The Rain Shadow: The Olympic Mountains protect Seattle from the full force of Pacific storms, but the effect is strongest in areas like Sequim (to the northwest) and tapers off as you move toward the Cascades.
Extreme Weather and Climate Shifts
While historically moderate, the 21st century has introduced more variability.
- Heat Waves: Once rare, "Heat Domes" have become more frequent, including the record-breaking 108°F (42°C) in 2021. Because most older homes lack air conditioning, these events are felt intensely by locals.
- Snow and Ice: Seattle averages about 5–6 inches of snow annually, but because of the hilly terrain and moist maritime air, even an inch of snow often turns into a sheet of ice (vertical skating), effectively shutting down the city.
Local Perspective
Seattleites are famous for their "no umbrella" policy. Because the rain is frequently a light mist accompanied by wind, umbrellas are often seen as impractical or a sign of a tourist. Instead, locals adapt with high-quality waterproof shells. When the first truly sunny day of spring hits (the "Big Reveal"), the city undergoes a collective mood shift, with parks like Gas Works and Alki Beach immediately reaching capacity.