Seattle weather in September
In September, Seattle sees average daytime highs of 69°F and overnight lows near 53°F, with 2.6 in of rain across 8.4 wet days and about 12.4 hours of daylight. It is the 3rd-warmest and 9th-wettest month of the year here.
Highs ease over the month, from about 72°F in the first days to 65°F by the end. The sky is clear or mostly clear about 41% of the time in September, and the air most often feels dry.
Daylight stretches from about 13 h 12 min at the start of September to 11 h 30 min by month's end. Set against the rest of the year, September is Seattle's 3rd-clearest and 10th-windiest month. For the whole year in context, see Seattle's year-round climate.
- Daytime high
- 69°
- 3rd warmest
- Overnight low
- 53°
- 10th coldest
- Rainfall
- 2.6 in
- 8.4 wet days
- Daylight
- 12 h 18 min
- 5:53 AM – 6:14 PM
- Cloud cover
- 48%
- 3rd clearest
- Wind
- 5 mph
- 10th windiest
- Solar energy
- 4.03 kWh/m²
- Travel score
- 6.8
- out of 10
Seattle is city in and county seat of King County, State of Washington, United States.
- Density
- 2,114/km²
- people per km²
- Founded
- 1851
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
Temperature in September
Highs ease over the month, from about 72°F in the first days to 65°F by the end.
A typical September day in Seattle reaches about 69°F in the afternoon and slips back to 53°F overnight — a 15°F spread between the day's warmth and the night's chill. On most days the high lands between 62°F and 77°F. Set against its neighbours, September runs about 6°F cooler than August and about 10°F warmer than October.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°F) | 72 | 72 | 72 | 72 | 72 | 71 | 71 | 71 | 71 | 70 | 70 | 70 | 70 | 69 | 69 | 69 | 69 | 68 | 68 | 68 | 67 | 67 | 67 | 67 | 66 | 66 | 66 | 65 | 65 | 65 |
| Avg low (°F) | 56 | 56 | 56 | 55 | 55 | 55 | 55 | 55 | 55 | 55 | 54 | 54 | 54 | 54 | 54 | 53 | 53 | 53 | 53 | 53 | 53 | 52 | 52 | 52 | 52 | 51 | 51 | 51 | 51 | 51 |
| Avg high (°F) | Avg low (°F) | |
|---|---|---|
| 1 | 72 | 56 |
| 2 | 72 | 56 |
| 3 | 72 | 56 |
| 4 | 72 | 55 |
| 5 | 72 | 55 |
| 6 | 71 | 55 |
| 7 | 71 | 55 |
| 8 | 71 | 55 |
| 9 | 71 | 55 |
| 10 | 70 | 55 |
| 11 | 70 | 54 |
| 12 | 70 | 54 |
| 13 | 70 | 54 |
| 14 | 69 | 54 |
| 15 | 69 | 54 |
| 16 | 69 | 53 |
| 17 | 69 | 53 |
| 18 | 68 | 53 |
| 19 | 68 | 53 |
| 20 | 68 | 53 |
| 21 | 67 | 53 |
| 22 | 67 | 52 |
| 23 | 67 | 52 |
| 24 | 67 | 52 |
| 25 | 66 | 52 |
| 26 | 66 | 51 |
| 27 | 66 | 51 |
| 28 | 65 | 51 |
| 29 | 65 | 51 |
| 30 | 65 | 51 |
Seattle weather by month
How September compares with the rest of the year at a glance. September is the 3rd-warmest and 9th-wettest month here — the current month is highlighted below.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | 46° / 38° | 6.9 | 18.4 | 2.2 | 8.7 | 1.0 |
| Feb | 49° / 39° | 4.7 | 14.5 | 1.8 | 9.9 | 1.6 |
| Mar | 52° / 40° | 5.5 | 17.5 | 0.8 | 11.6 | 2.3 |
| Apr | 57° / 44° | 4.5 | 14.9 | 0.1 | 13.3 | 3.5 |
| May | 64° / 49° | 3.0 | 12 | 0 | 14.9 | 5.3 |
| Jun | 68° / 53° | 2.3 | 9.5 | 0 | 15.7 | 6.3 |
| Jul | 74° / 57° | 1.0 | 5 | 0 | 15.4 | 7.9 |
| Aug | 75° / 58° | 1.3 | 4.8 | 0 | 14.1 | 8.0 |
| Sep | 69° / 53° | 2.6 | 8.4 | 0 | 12.4 | 6.8 |
| Oct | 59° / 47° | 5.3 | 14.1 | 0 | 10.6 | 4.2 |
| Nov | 50° / 42° | 7.6 | 18 | 0.6 | 9.1 | 1.9 |
| Dec | 45° / 38° | 7.0 | 17.6 | 2.1 | 8.3 | 0.8 |
Cloud cover in September
The sky is clear or mostly clear about 41% of the time in September.
Beyond those clear spells, partly cloudy skies cover about 16% of September, with mostly cloudy or overcast conditions the remaining 43%.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 60 | 60 | 61 | 61 | 61 | 61 | 60 | 60 | 59 | 58 | 58 | 57 | 56 | 57 | 56 | 56 | 55 | 56 | 56 | 55 | 55 | 55 | 54 | 54 | 54 | 54 | 54 | 52 | 52 | 51 |
| Cloudier (%) | 40 | 40 | 39 | 39 | 39 | 39 | 40 | 40 | 41 | 42 | 42 | 43 | 44 | 43 | 44 | 44 | 45 | 44 | 44 | 45 | 45 | 45 | 46 | 46 | 46 | 46 | 46 | 48 | 48 | 49 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| 1 | 60 | 40 |
| 2 | 60 | 40 |
| 3 | 61 | 39 |
| 4 | 61 | 39 |
| 5 | 61 | 39 |
| 6 | 61 | 39 |
| 7 | 60 | 40 |
| 8 | 60 | 40 |
| 9 | 59 | 41 |
| 10 | 58 | 42 |
| 11 | 58 | 42 |
| 12 | 57 | 43 |
| 13 | 56 | 44 |
| 14 | 57 | 43 |
| 15 | 56 | 44 |
| 16 | 56 | 44 |
| 17 | 55 | 45 |
| 18 | 56 | 44 |
| 19 | 56 | 44 |
| 20 | 55 | 45 |
| 21 | 55 | 45 |
| 22 | 55 | 45 |
| 23 | 54 | 46 |
| 24 | 54 | 46 |
| 25 | 54 | 46 |
| 26 | 54 | 46 |
| 27 | 54 | 46 |
| 28 | 52 | 48 |
| 29 | 52 | 48 |
| 30 | 51 | 49 |
Chance of precipitation in September
Seattle gets around 2.6 in of rain over 8.4 wet days in September. The line is the day-by-day chance of measurable precipitation.
Day to day, the chance of measurable rain averages around 28% and peaks near 31% on the wettest days. The odds climb toward the end of the month.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain chance (%) | 23 | 24 | 24 | 24 | 25 | 25 | 25 | 26 | 26 | 27 | 28 | 28 | 28 | 29 | 29 | 29 | 29 | 30 | 30 | 30 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 | 31 |
| Rain chance (%) | |
|---|---|
| 1 | 23 |
| 2 | 24 |
| 3 | 24 |
| 4 | 24 |
| 5 | 25 |
| 6 | 25 |
| 7 | 25 |
| 8 | 26 |
| 9 | 26 |
| 10 | 27 |
| 11 | 28 |
| 12 | 28 |
| 13 | 28 |
| 14 | 29 |
| 15 | 29 |
| 16 | 29 |
| 17 | 29 |
| 18 | 30 |
| 19 | 30 |
| 20 | 30 |
| 21 | 31 |
| 22 | 31 |
| 23 | 31 |
| 24 | 31 |
| 25 | 31 |
| 26 | 31 |
| 27 | 31 |
| 28 | 31 |
| 29 | 31 |
| 30 | 31 |
Humidity in September
Most of September feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
By dew point, September lands in the dry band about 71% of days. It rarely turns muggy — the humid and sticky bands barely register.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 58 | 59 | 60 | 60 | 61 | 62 | 63 | 65 | 66 | 67 | 68 | 69 | 69 | 70 | 71 | 71 | 72 | 73 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 |
| Comfortable (%) | 39 | 38 | 37 | 37 | 36 | 35 | 34 | 33 | 32 | 31 | 30 | 29 | 29 | 28 | 27 | 27 | 26 | 25 | 25 | 24 | 23 | 22 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 |
| Humid (%) | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
| Dry (%) | Comfortable (%) | Humid (%) | |
|---|---|---|---|
| 1 | 58 | 39 | 3 |
| 2 | 59 | 38 | 3 |
| 3 | 60 | 37 | 3 |
| 4 | 60 | 37 | 3 |
| 5 | 61 | 36 | 3 |
| 6 | 62 | 35 | 3 |
| 7 | 63 | 34 | 3 |
| 8 | 65 | 33 | 2 |
| 9 | 66 | 32 | 2 |
| 10 | 67 | 31 | 2 |
| 11 | 68 | 30 | 2 |
| 12 | 69 | 29 | 2 |
| 13 | 69 | 29 | 2 |
| 14 | 70 | 28 | 2 |
| 15 | 71 | 27 | 2 |
| 16 | 71 | 27 | 2 |
| 17 | 72 | 26 | 2 |
| 18 | 73 | 25 | 2 |
| 19 | 73 | 25 | 2 |
| 20 | 74 | 24 | 2 |
| 21 | 75 | 23 | 2 |
| 22 | 76 | 22 | 2 |
| 23 | 77 | 22 | 1 |
| 24 | 78 | 21 | 1 |
| 25 | 79 | 20 | 1 |
| 26 | 80 | 19 | 1 |
| 27 | 81 | 18 | 1 |
| 28 | 82 | 17 | 1 |
| 29 | 83 | 16 | 1 |
| 30 | 84 | 15 | 1 |
Wind in September
Winds average 5 mph in September.
Across September, daily wind ranges from about 4 mph on the calmest days to 5 mph at its breeziest. It stays fairly steady from day to day.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (mph) | 4 | 4 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 |
| Feels | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm |
| Wind speed (mph) | Feels | |
|---|---|---|
| 1 | 4 | calm |
| 2 | 4 | calm |
| 3 | 5 | calm |
| 4 | 5 | calm |
| 5 | 5 | calm |
| 6 | 5 | calm |
| 7 | 5 | calm |
| 8 | 5 | calm |
| 9 | 5 | calm |
| 10 | 5 | calm |
| 11 | 5 | calm |
| 12 | 5 | calm |
| 13 | 5 | calm |
| 14 | 5 | calm |
| 15 | 5 | calm |
| 16 | 5 | calm |
| 17 | 5 | calm |
| 18 | 5 | calm |
| 19 | 5 | calm |
| 20 | 5 | calm |
| 21 | 5 | calm |
| 22 | 5 | calm |
| 23 | 5 | calm |
| 24 | 5 | calm |
| 25 | 5 | calm |
| 26 | 5 | calm |
| 27 | 5 | calm |
| 28 | 5 | calm |
| 29 | 5 | calm |
| 30 | 5 | calm |
Sunrise & sunset in September
Daylight runs from about 13 h 12 min at the start of September to 11 h 30 min by month's end. The lit band spans sunrise to sunset each day.
Days shrink by about 102 minutes over September. Sunrise moves from 5:33 AM to 6:13 AM, and sunset from 6:45 PM to 5:44 PM.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 13.2 | 13.2 | 13.1 | 13.0 | 13.0 | 12.9 | 12.9 | 12.8 | 12.7 | 12.7 | 12.6 | 12.6 | 12.5 | 12.5 | 12.4 | 12.3 | 12.3 | 12.2 | 12.2 | 12.1 | 12.0 | 12.0 | 11.9 | 11.9 | 11.8 | 11.7 | 11.7 | 11.6 | 11.6 | 11.5 |
| Sunrise (AM) | 5:33 | 5:34 | 5:35 | 5:37 | 5:38 | 5:40 | 5:41 | 5:42 | 5:44 | 5:45 | 5:47 | 5:48 | 5:49 | 5:51 | 5:52 | 5:53 | 5:55 | 5:56 | 5:58 | 5:59 | 6:00 | 6:02 | 6:03 | 6:05 | 6:06 | 6:08 | 6:09 | 6:10 | 6:12 | 6:13 |
| Sunset (PM) | 6:45 | 6:43 | 6:41 | 6:39 | 6:37 | 6:35 | 6:33 | 6:31 | 6:29 | 6:27 | 6:24 | 6:22 | 6:20 | 6:18 | 6:16 | 6:14 | 6:12 | 6:10 | 6:07 | 6:05 | 6:03 | 6:01 | 5:59 | 5:57 | 5:55 | 5:52 | 5:50 | 5:48 | 5:46 | 5:44 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| 1 | 13.2 | 5:33 | 6:45 |
| 2 | 13.2 | 5:34 | 6:43 |
| 3 | 13.1 | 5:35 | 6:41 |
| 4 | 13.0 | 5:37 | 6:39 |
| 5 | 13.0 | 5:38 | 6:37 |
| 6 | 12.9 | 5:40 | 6:35 |
| 7 | 12.9 | 5:41 | 6:33 |
| 8 | 12.8 | 5:42 | 6:31 |
| 9 | 12.7 | 5:44 | 6:29 |
| 10 | 12.7 | 5:45 | 6:27 |
| 11 | 12.6 | 5:47 | 6:24 |
| 12 | 12.6 | 5:48 | 6:22 |
| 13 | 12.5 | 5:49 | 6:20 |
| 14 | 12.5 | 5:51 | 6:18 |
| 15 | 12.4 | 5:52 | 6:16 |
| 16 | 12.3 | 5:53 | 6:14 |
| 17 | 12.3 | 5:55 | 6:12 |
| 18 | 12.2 | 5:56 | 6:10 |
| 19 | 12.2 | 5:58 | 6:07 |
| 20 | 12.1 | 5:59 | 6:05 |
| 21 | 12.0 | 6:00 | 6:03 |
| 22 | 12.0 | 6:02 | 6:01 |
| 23 | 11.9 | 6:03 | 5:59 |
| 24 | 11.9 | 6:05 | 5:57 |
| 25 | 11.8 | 6:06 | 5:55 |
| 26 | 11.7 | 6:08 | 5:52 |
| 27 | 11.7 | 6:09 | 5:50 |
| 28 | 11.6 | 6:10 | 5:48 |
| 29 | 11.6 | 6:12 | 5:46 |
| 30 | 11.5 | 6:13 | 5:44 |
Solar energy in September
Average shortwave solar energy reaching the ground each day in September, about 4.03 kWh/m².
For context, solar energy here swings from a low near 0.88 kWh/m² to a high of 6.14 kWh/m² in July across the year — September's 4.03 kWh/m² falls in the middle.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 4.7 | 4.7 | 4.6 | 4.6 | 4.5 | 4.5 | 4.5 | 4.4 | 4.3 | 4.3 | 4.2 | 4.2 | 4.1 | 4.1 | 4.0 | 4.0 | 3.9 | 3.8 | 3.8 | 3.7 | 3.7 | 3.6 | 3.6 | 3.5 | 3.5 | 3.4 | 3.4 | 3.3 | 3.3 | 3.2 |
| Level | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| 1 | 4.7 | Bright |
| 2 | 4.7 | Bright |
| 3 | 4.6 | Bright |
| 4 | 4.6 | Bright |
| 5 | 4.5 | Bright |
| 6 | 4.5 | Bright |
| 7 | 4.5 | Bright |
| 8 | 4.4 | Bright |
| 9 | 4.3 | Bright |
| 10 | 4.3 | Bright |
| 11 | 4.2 | Bright |
| 12 | 4.2 | Bright |
| 13 | 4.1 | Bright |
| 14 | 4.1 | Bright |
| 15 | 4.0 | Bright |
| 16 | 4.0 | Moderate |
| 17 | 3.9 | Moderate |
| 18 | 3.8 | Moderate |
| 19 | 3.8 | Moderate |
| 20 | 3.7 | Moderate |
| 21 | 3.7 | Moderate |
| 22 | 3.6 | Moderate |
| 23 | 3.6 | Moderate |
| 24 | 3.5 | Moderate |
| 25 | 3.5 | Moderate |
| 26 | 3.4 | Moderate |
| 27 | 3.4 | Moderate |
| 28 | 3.3 | Moderate |
| 29 | 3.3 | Moderate |
| 30 | 3.2 | Moderate |
Hazard calendar for Seattle
None of Seattle's seasonal hazards are active in September. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.
Seattle's rainy season runs October–April, when most of the year's rain falls.
Is September a good time to visit Seattle?
Our two travel scores rate September for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).
September is a reasonable time to visit Seattle for sightseeing.
What to pack for Seattle in September
From September's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In September, Seattle sees daytime highs around 69°F and nights near 53°F. Worth packing: rain gear. About 8 days see rain.
Sea temperature near Seattle in September
The nearest coast averages about 53°F in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea at the nearest coast (about 44 mi away) is warmest in August at about 53°F and coldest in February near 46°F.
The water stays below 68°F all year — cool enough that most swimmers want a wetsuit.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°F) | 46 | 46 | 47 | 48 | 50 | 52 | 53 | 53 | 53 | 50 | 49 | 47 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing |
| Sea temperature (°F) | Comfort | |
|---|---|---|
| Jan | 46 | Bracing |
| Feb | 46 | Bracing |
| Mar | 47 | Bracing |
| Apr | 48 | Bracing |
| May | 50 | Bracing |
| Jun | 52 | Bracing |
| Jul | 53 | Bracing |
| Aug | 53 | Bracing |
| Sep | 53 | Bracing |
| Oct | 50 | Bracing |
| Nov | 49 | Bracing |
| Dec | 47 | Bracing |
UV index in Seattle in September
Clear-sky midday UV in September peaks around 4 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Seattle peaks around July 17 at about 8 (very high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near December 18 at about 1 (low).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 7 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 1 | 1 | 4 | 5 | 7 | 6 | 8 | 6 | 4 | 3 | 1 | 1 |
| Level | Low | Low | Moderate | Moderate | High | High | Very high | High | Moderate | Moderate | Low | Low |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 1 | Low |
| Feb | 1 | Low |
| Mar | 4 | Moderate |
| Apr | 5 | Moderate |
| May | 7 | High |
| Jun | 6 | High |
| Jul | 8 | Very high |
| Aug | 6 | High |
| Sep | 4 | Moderate |
| Oct | 3 | Moderate |
| Nov | 1 | Low |
| Dec | 1 | Low |
Air quality in Seattle in September
Average fine-particle pollution (PM2.5) through the year — so you can see where September falls, not just the annual average.
Air quality in Seattle is worst in September — around 22 µg/m³ PM2.5 (moderate), about 3.4× the cleanest month (December, 7 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 8 | 9 | 12 | 12 | 11 | 10 | 10 | 18 | 22 | 12 | 8 | 7 |
| Level | Good | Good | Moderate | Good | Good | Good | Good | Moderate | Moderate | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 8 | Good |
| Feb | 9 | Good |
| Mar | 12 | Moderate |
| Apr | 12 | Good |
| May | 11 | Good |
| Jun | 10 | Good |
| Jul | 10 | Good |
| Aug | 18 | Moderate |
| Sep | 22 | Moderate |
| Oct | 12 | Good |
| Nov | 8 | Good |
| Dec | 7 | Good |
Where is Seattle?
Seattle sits at 47.6°N, 122.3°W, 184 ft above sea level, in United States. The nearest listed city is Columbia City, 3.7 mi away.
Topography around Seattle
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Seattle.
Within 2 miles, the terrain around Seattle has only modest variations in elevation — a maximum elevation change of 482 ft around an average of 141 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 1,188 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 7,585 ft.
The land around Seattle is covered by artificial surfaces (57%) and water (25%) within 2 miles, water (41%), trees (34%) and artificial surfaces (22%) within 10 miles, and trees (73%) within 50 miles.
United States travel facts
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 100% of US
- price level, 2025
- GDP per capita
- $90,027
- 2025
- Happiness
- 6.8 / 10
- World Happiness, 2025
- Safe drinking water
- 98%
- of population, 2024
- Homicide rate
- 5.8
- per 100k, 2023
- Road deaths
- 12.7
- per 100k/yr, 2019
- Income group
- High
- World Bank
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Seattle (47.6062°, -122.3321°, elevation 184 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).