EnviroNearby

Strafford County, New Hampshire air quality history

Daily Air Quality Index summaries from EPA monitors in Strafford, New Hampshire, 1990–2003.

85%
Good days in 2003
38
Median daily AQI, 2003
4
Days above 100 in 2003
183
Days with an AQI in 2003 (of 365)

In 2003, EPA reported a daily Air Quality Index (AQI) for Strafford, New Hampshire on 183 days. 155 of those days (85%) were in the Good range, and the median daily AQI was 38. That median is about the same as the typical monitored county in New Hampshire (median 40 across 9 counties), and lower than the typical monitored U.S. county (44). The main pollutant was ozone on 183 days. Across the years with fuller monitoring, the share of Good days fell: an average of 89% in 1996–1998 versus 82% in 2001–2003.

EPA did not report an AQI for every day of 2003 here (183 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

The most recent year with data for this county is 2003; EPA's files for 2004–2025 contain no row for it, which usually means its monitors stopped reporting.

Years with fewer than 120 monitored days (1990, 1991, 1992, 1993, 1994, 1995) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Share of monitored days in each AQI category, by year0%25%50%75%100%1990: Good 56 of 56 days19901991: Good 58 of 59 days1991: Moderate 1 of 59 days19911992: Good 60 of 61 days1992: Moderate 1 of 61 days19921993: Good 59 of 60 days1993: Moderate 1 of 60 days19931994: Good 58 of 58 days19941995: Good 54 of 54 days19951996: Good 204 of 222 days1996: Moderate 12 of 222 days1996: Unhealthy for Sensitive Groups 4 of 222 days1996: Unhealthy 2 of 222 days19961997: Good 195 of 214 days1997: Moderate 12 of 214 days1997: Unhealthy for Sensitive Groups 6 of 214 days1997: Very Unhealthy 1 of 214 days19971998: Good 181 of 215 days1998: Moderate 27 of 215 days1998: Unhealthy for Sensitive Groups 7 of 215 days19981999: Good 196 of 225 days1999: Moderate 19 of 225 days1999: Unhealthy for Sensitive Groups 8 of 225 days1999: Unhealthy 2 of 225 days19992000: Good 223 of 239 days2000: Moderate 14 of 239 days2000: Unhealthy for Sensitive Groups 2 of 239 days20002001: Good 172 of 211 days2001: Moderate 29 of 211 days2001: Unhealthy for Sensitive Groups 9 of 211 days2001: Unhealthy 1 of 211 days20012002: Good 144 of 183 days2002: Moderate 26 of 183 days2002: Unhealthy for Sensitive Groups 9 of 183 days2002: Unhealthy 4 of 183 days20022003: Good 155 of 183 days2003: Moderate 24 of 183 days2003: Unhealthy for Sensitive Groups 4 of 183 days2003
  • Good
  • Moderate
  • Unhealthy for Sensitive Groups
  • Unhealthy
  • Very Unhealthy
  • Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median and 90th-percentile daily AQI, by year0501001990: 90th percentile AQI 291991: 90th percentile AQI 321992: 90th percentile AQI 281993: 90th percentile AQI 311994: 90th percentile AQI 231995: 90th percentile AQI 231996: 90th percentile AQI 471997: 90th percentile AQI 491998: 90th percentile AQI 671999: 90th percentile AQI 642000: 90th percentile AQI 482001: 90th percentile AQI 672002: 90th percentile AQI 772003: 90th percentile AQI 611990: Median AQI 171991: Median AQI 151992: Median AQI 151993: Median AQI 141994: Median AQI 101995: Median AQI 121996: Median AQI 311997: Median AQI 341998: Median AQI 371999: Median AQI 362000: Median AQI 312001: Median AQI 372002: Median AQI 392003: Median AQI 3819901991199219931994199519961997199819992000200120022003
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2003

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

PollutantDays as main pollutantShare of monitored days
Ozone183100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20031831552440003861129Ozone
20021831442694003977200Ozone
20012111722991003767197Ozone
20002392231420003148105Ozone
19992251961982003664172Ozone
19982151812770003767140Ozone
19972141951260103449203Ozone
19962222041242003147159Ozone
1995545400000122344PM10
1994585800000102344PM10
1993605910000143155PM10
1992616010000152864PM10
1991595810000153252PM10
1990565600000172942PM10

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

All monitored counties in New Hampshire

Source: U.S. EPA AirData, “Annual AQI by County” files for 1990–2003 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem