New Hampshire · County air quality · 2025
Coos County, New Hampshire
Median AQI 44 (Good). 81.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 44
- Median AQI
- 81.5%
- Good-air days
- 0
- Unhealthy days
- 60%
- Cleaner than US counties
Coos County's 2025 annual median AQI is 44 (Good), with 81.5% Good days
According to the U.S. EPA Air Quality System, Coos County, New Hampshire posted a 2025 median AQI of 44 (Good) across 345 monitored days, with 81.5% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Coos County's 81.5% Good-day share places it cleaner than 60% of US counties in 2025.
- Closest median-AQI peer
- Allegan County (63.9% Good, median AQI 44) is the closest nationwide median-AQI peer to Coos County.
- 2020–2025 trend
- Coos County's floor-qualifying Good-day share is worsening from 2020 to 2025 (92.6% → 81.4%).
- Median AQI
- Median AQI: 44
According to the 2025 EPA AQS county release on PlainAirData, Coos County, New Hampshire ranks #680 of 951 by median AQI (44) and #382 by good-day share (81.5%). Ponce County, Puerto Rico is #1 of 951 by median AQI (3, 91.4% Good days) at good-day-share #159 ≠ largest of 7 at 100.0% Good days #1 by good-day share (100.0%, median AQI 9) at median-AQI #7.
Annual release change
What changed in the 2025 EPA annual release
- Coos County's peak single-day AQI rose from 90 to 119 between the 2024 and 2025 EPA annual releases, a change of +29 points.
Data updated August 2026
- Good · 281 d · 81.4%
- Moderate · 60 d · 17.4%
- USG · 4 d · 1.2%
How did Coos County's air break down in 2025?
Across 345 monitored days, 281 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 119 (USG).
EPA AQS →Share of monitored days at AQI 0-50 (Good band).
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
Where Coos County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Coos County's Good-day share is 81.5% - cleaner than 60% of that comparison set.
Coos County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
81.5% Cleaner than 60% higher than 60% of 951 US counties
Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Coos County.
- Ozone · 310 days · 89.9%
- CO · 24 days · 7.0%
- PM2.5 · 11 days · 3.2%
2024 daily-monitor rhythm in Coos County
Month-by-month median AQI from EPA day-level county monitors (365 reported days in 2024). Jun posted the highest typical readings (median AQI 49, peak 87); May was cleanest at median 39. Summer months (Jun–Aug) averaged median AQI 48 vs 41 in Dec–Feb.
Five-year seasonal record
EPA day-level county files · 2020–20241,814 daily readings show a recurring local pattern: Mar has the highest matched-month median AQI (44), while Dec is lowest (39). Each cell is that month’s median daily AQI, not a current-air forecast.
Lower AQI is better. The colors summarize EPA AQI bands; gaps mean the county had no day-level record for that month.
Health Impact Assessment
Coos County's air quality is rated Good based on 81.5% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 81.5% of monitored days in 2025, with a median AQI of 44. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 310 of 345 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Coos County. Highest Good-day share: 2022 (97.5%, 350 of 359 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 339 | 27 | 0 | 0 | 43 | 74 |
| 2021 | 325 | 33 | 2 | 0 | 42 | 133 |
| 2022 | 350 | 9 | 0 | 0 | 40 | 64 |
| 2023 | 318 | 42 | 4 | 0 | 43 | 136 |
| 2024 | 296 | 69 | 0 | 0 | 44 | 90 |
| 2025 | 281 | 60 | 4 | 0 | 44 | 119 |
How does Coos County compare?
How Coos County compares
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Coos County, New Hampshire · 2020–2025
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
Every figure on PlainAirData is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.