Seattle weather, explained: rain, mountains, and a changing climate

A week after atmospheric rivers flooded parts of Western Washington, Seattle wakes to showery skies, cool mid 40s temperatures, and saturated ground on Friday, December 19, 2025. Rivers remain elevated in nearby counties, cleanup continues, and another round of weak systems is lined up over the Pacific, which means periodic rain and breezy intervals into early next week. For a city defined by drizzle, the stakes are higher now, as heavier bursts of rain and wind topple trees in wet soils, while smoke and heat increasingly shape summers.

What “Seattle weather” really means

Seattle sits between salt water and two mountain ranges, which shapes everything from daily showers to seasonal patterns. The Olympic Mountains wring moisture from incoming Pacific air, then cast a rain shadow that often spares the urban core from the very heaviest totals. The Cascade Range forces rising air and frequent winter storms, and when winds split around the Olympics and meet over Puget Sound, the convergence zone can park a narrow band of showers from north Seattle to Everett. The result is many days with light precipitation, and a few days with very heavy rain.

The long view, by the numbers

Below are 1991–2020 climate normals for Sea‑Tac Airport, the region’s official climate site. They show a cool, wet season from October through March, a distinct dry season in July and August, and mild temperatures year round.

• Annual snowfall averages 6.3 inches, most often in short, disruptive events that melt quickly.
• July and August together average about 1.6 inches of rain, which highlights how dry high summer can be.

Seattle gets its reputation from persistence, not totals. Many days have light rain, a few have a lot, and summer can go weeks with hardly any measurable precipitation.

Right now, and the week ahead

• Showers and sunbreaks dominate through the weekend, with daytime highs in the mid to upper 40s, and cooler nights in the upper 30s to low 40s.
• Given saturated soils after recent floods, even modest wind can bring down limbs, so plan for scattered power interruptions.
• Mountain passes remain vulnerable to rockfall and closures, and rivers east and north of the city stay elevated. Check road and river updates before travel.

Why the mountains decide so much

Olympic rain shadow

When westerly flow hits the Olympics, moisture condenses and falls on the windward slopes, then drier air descends toward central Puget Sound. Seattle often sits near this shadow, which can hold down totals in the city while heavier rain targets the Cascades and southwest coast.

Puget Sound convergence zone

When airflow splits around the Olympics and reconnects over the Sound, rising air creates a narrow band of showers or snow. Neighborhoods just a few miles apart can see very different conditions. In winter, the convergence zone can set up over north Seattle and bring quick accumulations, even when the rest of the city sees rain.

Winter 2025–26 outlook

• La Niña is in place this winter, and seasonal outlooks favor wetter conditions across the Pacific Northwest, and near normal to slightly cooler temperatures in parts of the northern tier.
• In practical terms for Seattle, that means more frequent storm days, a better chance of mountain snow that feeds rivers and ski areas, and a continued risk of heavy rain events that can trigger landslides and urban flooding.

The new normal, heavier bursts of rain

Meteorologists and climate scientists agree that a warmer atmosphere can hold more moisture, which heightens the odds of intense downpours. Analyses of hourly rainfall rates show increases since 1970 in most U.S. cities, including Seattle. This does not mean every storm is extreme, it does mean more storms can produce faster rain rates, which overwhelm drains and saturated hillsides.

Summer is drier, but no longer simple

• Summers remain mild and usually dry, yet heat waves have grown more dangerous. The 2021 heat dome set all time records and exposed gaps in cooling and shade, especially in neighborhoods with less tree canopy.
• Wildfire smoke is now a seasonal risk. Some years bring few smoky days, other years push air quality into unhealthy ranges for hours or days. Local agencies advise preparing a clean air room at home with a HEPA filter, and watching forecasts during late summer.

How to prepare, by season

• Late fall through winter
• Clear street drains near your home, and store extra batteries and a flashlight.
• If you live on or below a steep slope, review landslide guidance and have a plan to move to higher ground during prolonged heavy rain.
• Keep fuel or charge in your car, and know alternate routes if a pass or highway closes.
• Spring
• Expect changeable days, with showers and hail possible under cold upper level lows. Layer clothing, and start tracking snowmelt if you recreate on rivers.
• Summer
• Stock a small fan, a portable air conditioner or heat pump if feasible, and a HEPA filter. Identify a nearby cooling center or library for hot afternoons.
• Watch air quality maps for smoke intrusions, and plan morning outdoor activity when air is usually cleaner.

Quick facts to keep handy

• Annual precipitation at Sea‑Tac averages about 39 inches, spread over more than 150 days with measurable rain.
• November is typically the wettest month, July is the driest.
• Snow in the city is infrequent, but short events can snarl travel.
• The biggest flood and wind impacts often occur outside the urban core, even when Seattle stays in a rain shadow.

For the data minded

You can pull the same climate normals used above with a simple query.

```bash
curl "https://www.ncei.noaa.gov/access/services/data/v1?dataset=normals-monthly-1991-2020&stations=USW00024233&format=json"
```

How viewpoints differ

• Residents value the lighter, frequent rain and mild summers, yet worry about power outages, landslides, and smoke.
• Meteorologists point to topography, convergence, and Pacific storm tracks as the daily drivers.
• Climate and public health experts underscore rising extreme rain rates, flood exposure in lowlands and along rivers, growing heat risk, and inequities across neighborhoods.

Staying weather aware in Seattle does not require alarm, it rewards preparation, a good raincoat, and respect for the mountains and water that define the city.