Climate of Seattle, United States

Csb

Köppen-Geiger climate classification: Csb — Temperate, dry summer, warm summer.

Seattle has a mean annual temperature of 11.4 °C and receives 1037 mm of precipitation per year (1991–2020 climate normals). The warmest month is August with a mean temperature of 19.0 °C, while December is the coldest month at 5.0 °C. Most precipitation falls in December (161 mm); the driest month is July (21 mm).

Climate Diagram

Climate diagram for Seattle: monthly mean temperature (red line, left axis, °C) and monthly precipitation (blue bars, right axis, mm), 1991–2020 0 0 10 20 20 40 30 60 40 80 50 100 60 120 70 140 80 160 90 180 °C mm J F M A M J J A S O N D

Walter–Lieth diagram: blue bars show monthly precipitation (right axis, mm), the red line shows monthly mean temperature (left axis, °C). Scale: 1 °C ≡ 2 mm.

Climate Table

MonthMean temperature (°C)Precipitation (mm)
January5.2144.2
February6.1102.8
March7.7107.8
April10.179.3
May13.553.2
June16.044.6
July18.921.4
August19.028.4
September16.247.8
October11.697.9
November7.4148.2
December5.0161.3
Year11.41036.9

Live Forecast

Looking for the current weather instead of climate averages? Open the live forecast diagrams in WZ Diagrams — 15 weather models, ensemble spread, radar and more.

Data Source

Climate normals and Köppen-Geiger classification: Beck et al. (2023), Scientific Data 10, 724, CC BY 4.0. Period 1991–2020. Classification resolution ≈ 1 km; monthly climate data resolution ≈ 1 km (0.01°, Original 2023 release; predates the January 2026 correction), sampled at the grid cell containing the city coordinates (47.61°, -122.33°). Climate normals describe the long-term average, not current weather.