Median AQI
38
Good
New Hampshire · County air quality · 2025
Cheshire County, New Hampshire
Median AQI 38 (Good). 76.9% of monitored days rated Good, direct from EPA Air Quality System stations.
- 38
- Median AQI
- 76.9%
- Good-air days
- 0
- Unhealthy days
- 43%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Cheshire County's air is good on balance, more polluted than the median US county, a median AQI of 38 with 76.9% of 273 monitored days in the Good band, driven mainly by PM2.5.
- 38
- median AQI · Good
- 76.9%
- days rated Good
- PM2.5
- main pollutant
- 43%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 115.
Data updated July 2026
- Good · 210 d · 76.9%
- Moderate · 61 d · 22.3%
- USG · 2 d · 0.7%
How did Cheshire County's air break down in 2025?
Across 273 monitored days, 210 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 115 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 273 days monitored. Median AQI: 38 (Good).
Insights: Cheshire County, New Hampshire. EPA monitors recorded a median Air Quality Index of 38 across 273 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 210 (77%) fell in the Good band (AQI 0–50), 61 (22%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 58, while the worst single-day peak hit 115 (USG). Residents averaged about 23.1 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (149 days), Ozone (124 days). Across the 2020–2025 trend window, good days shifted by -89 and the median AQI moved +1 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 115, usg but never Unhealthy. Nearby counties show comparable readings: Belknap (87.9% good, AQI 34); Coos (85.4% good, AQI 40); Grafton (81.3% good, AQI 38); Hillsborough (82.5% good, AQI 38); Merrimack (95.9% good, AQI 38); Rockingham (82.5% good, AQI 39).
Air Quality Summary
Good Days
76.9%
210 of 273 monitored days
1.9pp vs 75% target
Max AQI Recorded
115
USG
Health Grade
Good
90th-pct AQI 58
Cheshire County, Good days share 76.9%
National avg
Share of monitored days at AQI 0-50 (Good band).
Cheshire County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 273 monitored days across EPA AQI categories.
Good
210
77%
Moderate
61
22%
USG
2
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Cheshire County.
- PM2.5 · 149 days · 54.6%
- Ozone · 124 days · 45.4%
Health Impact Assessment
Good
Cheshire County's air quality is rated Good based on 76.9% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 76.9% of monitored days in 2025, with a median AQI of 38. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 149 of 273 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Cheshire County. Best year: 2022 (304 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 299 | 67 | 0 | 0 | 37 | 78 |
| 2021 | 263 | 100 | 1 | 0 | 40 | 127 |
| 2022 | 304 | 61 | 0 | 0 | 37 | 84 |
| 2023 | 253 | 108 | 2 | 0 | 41 | 125 |
| 2024 | 302 | 64 | 0 | 0 | 36 | 93 |
| 2025 | 210 | 61 | 2 | 0 | 38 | 115 |
How does Cheshire County compare?
How Cheshire County compares
Good-day share about average
Cheshire County 76.9%
Belknap County, New Hampshire 87.9%
US average 76.5%
Median AQI about average
Cheshire County 38
Belknap County, New Hampshire 34
US average 38
Unhealthy days / yr about average
Cheshire County 0
Belknap County, New Hampshire 0
US average 0
Other Counties in New Hampshire
Air quality comparison for nearby counties in New Hampshire.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Cheshire County.
Adams County, Illinois
AQI 38 · 94.4% good
Anoka County, Minnesota
AQI 38 · 82.1% good
Atlantic County, New Jersey
AQI 38 · 79.6% good
Avery County, North Carolina
AQI 38 · 93.9% good
Barnstable County, Massachusetts
AQI 38 · 92.5% good
Bay County, Michigan
AQI 38 · 71.8% good
What Cheshire County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 38 means for exposure. Health guidance
- See how Cheshire County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Cheshire County with its New Hampshire neighbours before drawing a conclusion about the region. All of New Hampshire
Based on 273 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Cheshire County, New Hampshire? ▼
Cheshire County has a median Air Quality Index (AQI) of 38, rated "Good." 76.9% of monitored days (210 out of 273) had good air quality in 2025.
What is the main pollutant in Cheshire County? ▼
The primary pollutant in Cheshire County is Fine Particles (PM2.5), which was the main AQI driver on 149 days (55% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Cheshire County have? ▼
In 2025, Cheshire County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 115.
Is the air quality in Cheshire County getting better or worse? ▼
Air quality in Cheshire County is worsening based on 5-year trends (2020-2025). Best year: 2022 with 304 good days. Worst year: 2025 with 210 good days.
What does AQI 38 mean for health? ▼
Cheshire County's median AQI of 38 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Cheshire County compare to other counties in New Hampshire? ▼
Cheshire County has 76.9% good air days. Nearby counties in New Hampshire: Belknap (87.9% good), Coos (85.4% good), Grafton (81.3% good), Hillsborough (82.5% good), Merrimack (95.9% good), Rockingham (82.5% good).
What is the 90th percentile AQI in Cheshire County? ▼
The 90th percentile AQI for Cheshire County is 58, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 115 (USG).
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.
Every figure on PlainAir 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.