Merrimack, New Hampshire Air Quality
Merrimack County, New Hampshire (NH)
↑ Worseningover 10 years
How Merrimack, New Hampshire Air Quality Compares
Merrimack, New Hampshire's median AQI of 39is 5% better than the national average of 41. Air quality has worsened by 6 AQI points over the past decade. The area rarely experiences unhealthy air quality days. The primary pollutant of concern is Ground-Level Ozone.
Merrimack, New Hampshire Air Quality: The Full Picture
Merrimack, New Hampshire (Merrimack County) holds an AirHistory Air Quality Grade of C (fair, scoring 62 out of 100), built from 10 years of EPA Air Quality System monitoring. Its median AQI rose 6 points between 2014 (33) and 2023 (39), and the five-year median now sits at 37 — inside the "Good" band on the EPA scale.
The pollutant driving most of the area's AQI readings is Ground-Level Ozone. In 2023, it set the daily AQI on 213 of 213 monitored days (100% of the year), making it the controlling pollutant for the C grade. The single worst reading logged that year hit an AQI of 100 (Moderate), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 48.
In 2023, Merrimack County recorded 197 "Good" air days (92% of the 213 days with valid AQI data), 16 "Moderate" days, and 0 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged 1 days that crossed into "Unhealthy for Sensitive Groups" or worse — about 0 per year.
The decade-long trend is worsening: median AQI has been climbing by roughly 0.70 points per year. The cleanest year in the record was 2016 (median AQI 31), and the most polluted was 2023 (median AQI 39). Because the data come straight from federally certified EPA monitors, these figures track the New Hampshire county the monitors physically sit in rather than a city boundary.
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10-Year AQI Trend
The solid line shows the median AQI each year. The dashed line shows the 90th percentile (worst 10% of days). Air quality in this area has been declining over the past decade.
Air Quality Day Breakdown
Number of days per year in each EPA AQI category. Green = Good (AQI 0-50), Yellow = Moderate (51-100), Orange = Unhealthy for Sensitive Groups (101-150), Red = Unhealthy or worse (151+).
Year-by-Year Data
| Year | Median AQI | 90th Pct | Max AQI | Good Days | Moderate | Unhealthy+ | Pollutant |
|---|---|---|---|---|---|---|---|
| 2023 | 39 | 48 | 100 | 197 | 16 | 0 | Ozone |
| 2022 | 36 | 46 | 84 | 205 | 7 | 0 | Ozone |
| 2021 | 36 | 47 | 101 | 200 | 13 | 1 | Ozone |
| 2020 | 38 | 44 | 74 | 209 | 4 | 0 | Ozone |
| 2019 | 36 | 44 | 61 | 206 | 4 | 0 | Ozone |
| 2018 | 38 | 47 | 87 | 203 | 10 | 0 | Ozone |
| 2017 | 32 | 45 | 90 | 352 | 12 | 0 | Ozone |
| 2016 | 31 | 44 | 84 | 344 | 14 | 0 | Ozone |
| 2015 | 33 | 45 | 105 | 354 | 7 | 1 | Ozone |
| 2014 | 33 | 52 | 101 | 259 | 37 | 1 | Ozone |
What This Means for Merrimack County Residents
Merrimack, New Hampshire has received an Air Quality Grade of C (62/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 39 falls in the "Good" range.
Concerning trends show air quality has been declining, with the median AQI rising by 6 points over the monitoring period. This could be driven by increased development, wildfire smoke, or industrial activity.
The primary pollutant affecting this area is Ground-Level Ozone. Over the past 5 years, this area has averaged 0 unhealthy air quality days per year, days when sensitive groups (children, elderly, those with respiratory conditions) should limit outdoor activity. The American Lung Association's State of the Air report provides additional context on long-term health risks from air pollution exposure.
Frequently Asked Questions
Merrimack, New Hampshire has a current median AQI of 39, which falls in the "Good" range. The area has received an Air Quality Grade of C (62/100) based on 10 years of EPA monitoring data.
Air quality in Merrimack, New Hampshire is worsening over the past decade. The median AQI has changed by +6 points from 2014 to 2023.
Merrimack, New Hampshire averages 0 unhealthy air quality days per year over the past 5 years. On these days, sensitive groups including children, the elderly, and those with respiratory conditions should limit outdoor activity.
The primary pollutant affecting Merrimack, New Hampshire is Ground-Level Ozone. This is the dominant contributor to elevated AQI readings in the Merrimack County area.
Merrimack, New Hampshire averages 0 unhealthy air days per year. This is relatively low, making it a reasonable choice for asthma sufferers. The primary pollutant is Ground-Level Ozone, which is a known asthma trigger.
With a median AQI of 39 (Good), outdoor exercise in Merrimack, New Hampshire is generally safe year-round. Merrimack, New Hampshire averages 0 days per year when athletes should move workouts indoors.