Seattle, Washington, United States Historical Air Quality Analysis
Dive into detailed Air Quality Insights with historical data, monthly patterns, and yearly trends at your fingertips!
September Air Quality Analysis
Seattle, Washington, United States
AQI Trends: Highest and Lowest
Same Day Analysis (1st September ):
On this day, AQI across the 5 years varied significantly: 2025 ranks 3rd highest AQI at 42 of Good air quality, showing improvement over 2024 and 2022 on the same day.
Download 2024 Annual Data
World Air Quality Report

Day & Night AQI Trend: 1st Sep - 2nd Sep 2025
Seattle, Washington, United States
6 AM1st Sep 2025
8 PM
5 AM2nd Sep 2025
42AQI
35AQI
50AQI
42AQI
In the last 24 hours,
Seattle's AQI reached its highest point of 50 at 1 AM during the Night, while the lowest point, 35, was recorded at 11 AM during the Day between 1st Sep and 2nd Sep 2025.
Day & Night AQI Trend : Aug - Sep 2025
Seattle, Washington, United States
--°C/°C
18°C15/21°C
20°C16/24°C
18°C16/21°C
18°C14/24°C
19°C14/26°C
21°C15/29°C
24°C18/32°C
24°C19/31°C
28°C22/36°C
20°C16/22°C
18°C16/22°C
19°C15/22°C
20°C17/24°C
21°C16/27°C
20°C17/25°C
21°C17/26°C
19°C16/24°C
19°C14/25°C
23°C16/33°C
25°C19/34°C
27°C20/35°C
26°C20/35°C
26°C20/34°C
23°C19/27°C
23°C18/30°C
20°C17/22°C
19°C14/24°C
19°C14/25°C
20°C17/23°C
21°C16/29°C
36AQI
33AQI
36AQI
36AQI
2025 Days Vs Air Quality
Seattle, Washington, United States
95%
233
5%
11
Total number of days with different AQI categories in last 246 days in 2025 (119 days remaining)
Under WHO’s Safe Air Quality Limits: 95%
Health Risk Level:
Very Low
In 2025, 95% of 246 days were within WHO’s safe air quality limits. The risk of health issues is Very Low, but health impacts are still unclear.
Annual Air Quality Insights
Seattle, Washington, United States
AQI levels in 2025
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
31AQI
36AQI
25AQI
31AQI
28AQI
23AQI
37AQI
33AQI
45AQI
34AQI
30AQI
47AQI
45AQI
44AQI
46AQI
43AQI
38AQI
37AQI
44AQI
46AQI
57AQI
48AQI
55AQI
47AQI
40AQI
51AQI
48AQI
55AQI
61AQI
54AQI
30AQI
21AQI
21AQI
23AQI
28AQI
21AQI
25AQI
29AQI
29AQI
37AQI
30AQI
24AQI
28AQI
32AQI
42AQI
42AQI
25AQI
26AQI
27AQI
22AQI
22AQI
29AQI
26AQI
22AQI
28AQI
19AQI
33AQI
28AQI
39AQI
47AQI
35AQI
30AQI
23AQI
25AQI
24AQI
28AQI
27AQI
25AQI
21AQI
25AQI
24AQI
21AQI
22AQI
24AQI
22AQI
24AQI
21AQI
20AQI
18AQI
23AQI
21AQI
21AQI
19AQI
26AQI
27AQI
20AQI
18AQI
20AQI
22AQI
21AQI
22AQI
23AQI
29AQI
33AQI
36AQI
29AQI
18AQI
16AQI
19AQI
28AQI
22AQI
22AQI
21AQI
24AQI
25AQI
25AQI
26AQI
29AQI
28AQI
22AQI
19AQI
22AQI
26AQI
33AQI
42AQI
46AQI
34AQI
23AQI
20AQI
21AQI
33AQI
34AQI
17AQI
20AQI
20AQI
28AQI
26AQI
21AQI
24AQI
25AQI
19AQI
20AQI
26AQI
26AQI
25AQI
19AQI
20AQI
16AQI
20AQI
15AQI
17AQI
22AQI
20AQI
21AQI
20AQI
17AQI
22AQI
27AQI
18AQI
23AQI
22AQI
23AQI
23AQI
24AQI
22AQI
26AQI
28AQI
34AQI
36AQI
37AQI
43AQI
46AQI
42AQI
34AQI
26AQI
27AQI
28AQI
23AQI
20AQI
20AQI
20AQI
21AQI
22AQI
25AQI
37AQI
31AQI
22AQI
19AQI
26AQI
26AQI
26AQI
27AQI
20AQI
20AQI
22AQI
41AQI
28AQI
24AQI
27AQI
19AQI
21AQI
26AQI
21AQI
28AQI
24AQI
29AQI
40AQI
45AQI
42AQI
31AQI
28AQI
33AQI
28AQI
32AQI
29AQI
24AQI
29AQI
31AQI
31AQI
30AQI
33AQI
30AQI
29AQI
30AQI
29AQI
50AQI
38AQI
22AQI
20AQI
27AQI
27AQI
32AQI
34AQI
33AQI
32AQI
23AQI
17AQI
14AQI
19AQI
25AQI
25AQI
24AQI
27AQI
36AQI
41AQI
52AQI
59AQI
57AQI
55AQI
47AQI
55AQI
44AQI
50AQI
42AQI
42AQI
28AQI
24AQI
26AQI
22AQI
28AQI
29AQI
35AQI
42AQI
No. of days
202529AQI
Highest AQI recorded in
September42AQI
Lowest AQI recorded in
May22AQI
202428AQI
Highest AQI recorded in
September35AQI
Lowest AQI recorded in
February21AQI
202332AQI
Highest AQI recorded in
August39AQI
Lowest AQI recorded in
April25AQI
202233AQI
Highest AQI recorded in
October65AQI
Lowest AQI recorded in
May22AQI
202127AQI
Highest AQI recorded in
August34AQI
Lowest AQI recorded in
May20AQI
202035AQI
Highest AQI recorded in
September82AQI
Lowest AQI recorded in
June23AQI
Most & Least Polluted Years Over the Last 6 Years
Seattle's annual 2025 AQI (29) shows an average percentage change of -5.1% (improved AQI) compared to previous years: 2020 (35), 2021 (27), 2022 (33), 2023 (32), 2024 (28).