Seattle weather by month — averages, rainfall & climate trends
Framed by Puget Sound and the Olympic and Cascade ranges, the Emerald City is famous for its soft grey drizzle and deep evergreen forests — a maritime Pacific Northwest climate of mild, damp winters and bright, dry summers. Average temperatures and rainfall by month, a climate graph, today's conditions versus the long-term average, and how the climate has shifted since 1940 — all on one page for Seattle, United States.
Today vs average
+2.3°Cwarmer than usual
How it’s changed
Right now
What it's doing today vs the historical average for this date.
Right now
21.6°
27°13°31°17°
36°17°35°18°29°15°27°15°
28°13°On this date — July 20
Warmer than usual · 2.3°C above the average high
- Record high: 35.5° · 1994
- Record low: 10.5° · 1974
- One year ago: 21.6°
Every July 20 in history — coldest to hottest
Dots show daily highs (top) and lows (bottom) for each July 20 on record (n = 87). Outlined dots are today's forecast.
Area we sample
Each city's history comes from one ERA5 grid cell — about 28 km across, shown by the dashed box. Near mountains or coasts, conditions can vary across the cell.
Location & data
Historical weather for Seattle is sampled from the ECMWF ERA5 reanalysis at 47.61°N, 122.33°W, with daily records since 1940.
- Coordinates
- 47.61°N, 122.33°W
- Time zone
- America/Los Angeles
- Period
- 1940–2026
- Data source
- ERA5 (ECMWF)
Last 30 days
12 of the last 31 days were warmer than the historical average for that date. Average difference: +0.0°C.
Each bar is one day, from morning low to afternoon high. Warm-colored bars are days whose mean ran above average; cool bars ran below. The dot inside the bar is the daily mean. The shaded band is the typical 10–90% range expected for that date. Average = the day's mean temperature averaged across every year of record (1940–2026) for that calendar date.
This date over the years
One dot per year — the mean temperature on this calendar date. Dots are warmer or cooler than the long-term average (dashed line); the shaded band is the typical 10–90% range, and the highlighted dot is today's forecast. Based on ERA5 reanalysis — modelled estimates, not station readings.
Weather by month
Average temperatures and rainfall for each month — what a typical year looks like, from the full record.Climate overview
Seattle has a warm-summer Mediterranean climate (Köppen Csb), often also described as oceanic. The Pacific Ocean, Puget Sound and Lake Washington moderate its temperatures into small seasonal swings, while the Olympic Mountains to the west cast a partial rain shadow over the city. From October through March the Aleutian Low steers a procession of Pacific storms across the region, bringing the long, cloudy, drizzly wet season for which Seattle is known; summers are comparatively dry and bright under the North Pacific High.
The city's signature hazards are wind and water rather than heat — major windstorms such as the Columbus Day Storm of 1962 and the 2006 Hanukkah Eve storm caused widespread damage and power outages. More recent extremes include the record-breaking Pacific Northwest heat wave of late June 2021 and an unusually long rainless stretch in the summer of 2017. Over the past century the climate has warmed and air conditioning has spread from a rarity to most households, while heavy-rainfall events and sea level are both documented as rising.
August brings the year's peak warmth: daily means of 18.6°C, with afternoons typically reaching 24.5°C. In January, daily means drop to roughly 4.6°C, with nights dipping to 2.7°C.
The yearly total for Seattle comes to about 1423 mm; monthly amounts range from 30 mm in July up to 201 mm in November. Precipitation falls on roughly 170 days in a typical year.
The record here starts in 1940, and since then the annual mean in Seattle has climbed 1.2°C from the first ten years to the last ten. Frost days have thinned out, from around 20 a year in the first decade to about 12 now.
Climate graph (climograph)
August is the warmest month, January the coolest — a yearly swing of 14°C. Wettest month: November (~201 mm). Whole year averages ~1423 mm of rain.
Bars = average monthly rainfall (right axis). Lines = average daily high and low (left axis). Average = each month's value averaged across every year of record (1940–2026).
Monthly wind
Average daily peak wind at 10 m, by month.
Monthly solar energy
Average daily incoming solar energy in megajoules per square metre — a measured proxy for how sunny the month is.
Seattle month by month — what to expect
Typical conditions for each month, averaged across the full record (since 1940). Daylight is the time from sunrise to sunset. Record high/low are the most extreme values in the ERA5 dataset (modelled since 1940), so they can differ from official weather-station readings.
| Month | Avg high | Avg low | Rain | Daylight | Record high | Record low |
|---|---|---|---|---|---|---|
| January | 7.2° | 2.7° | 189 mm | 8.6 h | 16.3° (2005) | -15.8° (1950) |
| February | 9.1° | 3.4° | 144 mm | 10.0 h | 18.8° (1986) | -14.8° (1950) |
| March | 11.4° | 4.4° | 144 mm | 11.6 h | 23.9° (2004) | -10.3° (1955) |
| April | 14.4° | 6.2° | 112 mm | 13.4 h | 29.2° (2016) | -1.3° (1968) |
| May | 18.1° | 9.1° | 83 mm | 14.9 h | 33.5° (1972) | -0.1° (1954) |
| June | 21.0° | 11.9° | 66 mm | 15.8 h | 38.3° (2021) | 4.8° (1976) |
| July | 24.4° | 14.0° | 30 mm | 15.4 h | 37.5° (1941) | 7.2° (1962) |
| August | 24.5° | 14.2° | 38 mm | 14.1 h | 35.6° (1978) | 7.3° (1980) |
| September | 21.3° | 12.0° | 73 mm | 12.3 h | 33.1° (1988) | 2.6° (1972) |
| October | 15.7° | 8.6° | 140 mm | 10.6 h | 28.9° (1987) | -4.1° (1971) |
| November | 10.2° | 5.4° | 201 mm | 9.0 h | 19.3° (2016) | -14.5° (1985) |
| December | 7.4° | 3.4° | 201 mm | 8.2 h | 16.1° (1980) | -15.0° (1968) |
How it has changed
Year-by-year signals from 1940 to today.Climate stripes
Annual mean shifted from 1940–1949 to 2016–2025 by +1.2°C.
Each vertical stripe is one year. Color encodes how much that year's annual mean differed from the long-term average. Average = each year's annual mean compared to the average of all years (1940–2026). cooler ← → warmer
Annual mean temperature
Long-term trend: +0.17°C per decade.
One point per year — the temperature averaged across the whole year. The dashed line is the least-squares long-term trend. Based on ERA5 reanalysis — modelled estimates, not station readings.
Seasonal warming
Dec–Feb is warming fastest: +0.22°C per decade.
Each faint line is one three-month period's average per year; the bold dashed line is its long-term trend. Different parts of the year often warm at different rates. Based on ERA5 reanalysis — modelled estimates, not station readings.
Hot days vs frost days
Days ≥ 30°C per year: 5.1 early in the record → 5.4 recently. Frost days: 22 → 12.
Thin lines are raw yearly counts; thick lines are the smoothed trend that removes year-to-year noise. The hot-day threshold is auto-picked per city so the line actually moves. Average = a centered 5-year rolling average to smooth weather noise.
Yearly hot & cold extremes
All-time high in 2021, all-time low in 1950: 38.3°C / -15.8°C.
One point per year — the single hottest and coldest day recorded that year.
Annual rainfall
~1423 mm/year on average. Last decade ran −4% vs that average. Long-term trend: −11 mm per decade.
One bar per year of total rainfall. Dashed line is the long-term average. Average = the average annual rainfall across every year of record (1940–2026).
Day-by-day grid
Each tiny square is one calendar day across the full record — ~30,000 days per city. Use the mode switch above the chart: Anomaly colors each day by how far it ran from the historical average for that date (red = warmer, blue = cooler), Daily mean temp shows the absolute mean temperature for the day (useful to see seasons and heatwaves), and Precipitation shows daily rainfall (useful to spot wet/dry seasons and droughts). Average = the long-term average for that calendar date (1940–2026).