EnviroNearby

Guilford County, North Carolina air quality history

Daily Air Quality Index summaries from EPA monitors in Guilford, North Carolina, 1980–2025.

75%
Good days in 2025
41
Median daily AQI, 2025
0
Days above 100 in 2025
365
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Guilford, North Carolina on 365 days. 274 of those days (75%) were in the Good range, and the median daily AQI was 41. That median is about the same as the typical monitored county in North Carolina (median 39 across 33 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 213 days. Across the years with fuller monitoring, the share of Good days rose: an average of 56% in 1980–1982 versus 64% in 2023–2025.

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%1980: Good 110 of 197 days1980: Moderate 48 of 197 days1980: Unhealthy for Sensitive Groups 27 of 197 days1980: Unhealthy 12 of 197 days19801981: Good 138 of 212 days1981: Moderate 48 of 212 days1981: Unhealthy for Sensitive Groups 23 of 212 days1981: Unhealthy 3 of 212 days1982: Good 78 of 161 days1982: Moderate 55 of 161 days1982: Unhealthy for Sensitive Groups 20 of 161 days1982: Unhealthy 7 of 161 days1982: Very Unhealthy 1 of 161 days1983: Good 110 of 206 days1983: Moderate 67 of 206 days1983: Unhealthy for Sensitive Groups 23 of 206 days1983: Unhealthy 6 of 206 days1984: Good 109 of 200 days1984: Moderate 54 of 200 days1984: Unhealthy for Sensitive Groups 27 of 200 days1984: Unhealthy 10 of 200 days1985: Good 81 of 183 days1985: Moderate 64 of 183 days1985: Unhealthy for Sensitive Groups 35 of 183 days1985: Unhealthy 3 of 183 days19851986: Good 88 of 183 days1986: Moderate 56 of 183 days1986: Unhealthy for Sensitive Groups 25 of 183 days1986: Unhealthy 13 of 183 days1986: Very Unhealthy 1 of 183 days1987: Good 110 of 221 days1987: Moderate 72 of 221 days1987: Unhealthy for Sensitive Groups 32 of 221 days1987: Unhealthy 7 of 221 days1988: Good 79 of 232 days1988: Moderate 76 of 232 days1988: Unhealthy for Sensitive Groups 41 of 232 days1988: Unhealthy 24 of 232 days1988: Very Unhealthy 12 of 232 days1989: Good 162 of 263 days1989: Moderate 82 of 263 days1989: Unhealthy for Sensitive Groups 17 of 263 days1989: Unhealthy 2 of 263 days1990: Good 231 of 365 days1990: Moderate 91 of 365 days1990: Unhealthy for Sensitive Groups 32 of 365 days1990: Unhealthy 10 of 365 days1990: Very Unhealthy 1 of 365 days19901991: Good 270 of 364 days1991: Moderate 77 of 364 days1991: Unhealthy for Sensitive Groups 15 of 364 days1991: Unhealthy 2 of 364 days1992: Good 291 of 366 days1992: Moderate 66 of 366 days1992: Unhealthy for Sensitive Groups 9 of 366 days1993: Good 244 of 365 days1993: Moderate 65 of 365 days1993: Unhealthy for Sensitive Groups 43 of 365 days1993: Unhealthy 13 of 365 days1994: Good 258 of 365 days1994: Moderate 73 of 365 days1994: Unhealthy for Sensitive Groups 29 of 365 days1994: Unhealthy 5 of 365 days1995: Good 256 of 362 days1995: Moderate 78 of 362 days1995: Unhealthy for Sensitive Groups 24 of 362 days1995: Unhealthy 4 of 362 days19951996: Good 270 of 366 days1996: Moderate 74 of 366 days1996: Unhealthy for Sensitive Groups 20 of 366 days1996: Unhealthy 2 of 366 days1997: Good 257 of 365 days1997: Moderate 82 of 365 days1997: Unhealthy for Sensitive Groups 23 of 365 days1997: Unhealthy 3 of 365 days1998: Good 246 of 364 days1998: Moderate 59 of 364 days1998: Unhealthy for Sensitive Groups 44 of 364 days1998: Unhealthy 15 of 364 days1999: Good 99 of 364 days1999: Moderate 209 of 364 days1999: Unhealthy for Sensitive Groups 40 of 364 days1999: Unhealthy 16 of 364 days2000: Good 79 of 366 days2000: Moderate 251 of 366 days2000: Unhealthy for Sensitive Groups 28 of 366 days2000: Unhealthy 8 of 366 days20002001: Good 79 of 365 days2001: Moderate 261 of 365 days2001: Unhealthy for Sensitive Groups 21 of 365 days2001: Unhealthy 4 of 365 days2002: Good 91 of 365 days2002: Moderate 224 of 365 days2002: Unhealthy for Sensitive Groups 32 of 365 days2002: Unhealthy 16 of 365 days2002: Very Unhealthy 2 of 365 days2003: Good 103 of 364 days2003: Moderate 246 of 364 days2003: Unhealthy for Sensitive Groups 13 of 364 days2003: Unhealthy 1 of 364 days2003: Very Unhealthy 1 of 364 days2004: Good 105 of 366 days2004: Moderate 253 of 366 days2004: Unhealthy for Sensitive Groups 8 of 366 days2005: Good 93 of 365 days2005: Moderate 250 of 365 days2005: Unhealthy for Sensitive Groups 20 of 365 days2005: Unhealthy 2 of 365 days20052006: Good 126 of 336 days2006: Moderate 180 of 336 days2006: Unhealthy for Sensitive Groups 28 of 336 days2006: Unhealthy 2 of 336 days2007: Good 110 of 365 days2007: Moderate 215 of 365 days2007: Unhealthy for Sensitive Groups 36 of 365 days2007: Unhealthy 4 of 365 days2008: Good 100 of 365 days2008: Moderate 255 of 365 days2008: Unhealthy for Sensitive Groups 8 of 365 days2008: Unhealthy 2 of 365 days2009: Good 161 of 364 days2009: Moderate 199 of 364 days2009: Unhealthy for Sensitive Groups 4 of 364 days2010: Good 136 of 364 days2010: Moderate 209 of 364 days2010: Unhealthy for Sensitive Groups 18 of 364 days2010: Unhealthy 1 of 364 days20102011: Good 154 of 361 days2011: Moderate 196 of 361 days2011: Unhealthy for Sensitive Groups 11 of 361 days2012: Good 173 of 364 days2012: Moderate 183 of 364 days2012: Unhealthy for Sensitive Groups 7 of 364 days2012: Unhealthy 1 of 364 days2013: Good 223 of 357 days2013: Moderate 133 of 357 days2013: Unhealthy for Sensitive Groups 1 of 357 days2014: Good 182 of 353 days2014: Moderate 171 of 353 days2015: Good 216 of 364 days2015: Moderate 147 of 364 days2015: Unhealthy for Sensitive Groups 1 of 364 days20152016: Good 210 of 366 days2016: Moderate 152 of 366 days2016: Unhealthy for Sensitive Groups 4 of 366 days2017: Good 229 of 365 days2017: Moderate 135 of 365 days2017: Unhealthy for Sensitive Groups 1 of 365 days2018: Good 238 of 355 days2018: Moderate 116 of 355 days2018: Unhealthy for Sensitive Groups 1 of 355 days2019: Good 244 of 365 days2019: Moderate 121 of 365 days2020: Good 288 of 365 days2020: Moderate 77 of 365 days20202021: Good 245 of 365 days2021: Moderate 120 of 365 days2022: Good 223 of 365 days2022: Moderate 142 of 365 days2023: Good 183 of 365 days2023: Moderate 178 of 365 days2023: Unhealthy for Sensitive Groups 4 of 365 days2024: Good 249 of 366 days2024: Moderate 116 of 366 days2024: Unhealthy for Sensitive Groups 1 of 366 days2025: Good 274 of 365 days2025: Moderate 91 of 365 days2025
  • 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 year0501001502001980: 90th percentile AQI 1331981: 90th percentile AQI 1081982: 90th percentile AQI 1221983: 90th percentile AQI 1121984: 90th percentile AQI 1331985: 90th percentile AQI 1261986: 90th percentile AQI 1431987: 90th percentile AQI 1151988: 90th percentile AQI 1721989: 90th percentile AQI 931990: 90th percentile AQI 1051991: 90th percentile AQI 841992: 90th percentile AQI 711993: 90th percentile AQI 1221994: 90th percentile AQI 971995: 90th percentile AQI 971996: 90th percentile AQI 841997: 90th percentile AQI 901998: 90th percentile AQI 1151999: 90th percentile AQI 1152000: 90th percentile AQI 1002001: 90th percentile AQI 932002: 90th percentile AQI 1192003: 90th percentile AQI 842004: 90th percentile AQI 802005: 90th percentile AQI 932006: 90th percentile AQI 982007: 90th percentile AQI 1012008: 90th percentile AQI 822009: 90th percentile AQI 682010: 90th percentile AQI 802011: 90th percentile AQI 822012: 90th percentile AQI 692013: 90th percentile AQI 602014: 90th percentile AQI 642015: 90th percentile AQI 612016: 90th percentile AQI 672017: 90th percentile AQI 612018: 90th percentile AQI 642019: 90th percentile AQI 612020: 90th percentile AQI 552021: 90th percentile AQI 622022: 90th percentile AQI 592023: 90th percentile AQI 672024: 90th percentile AQI 592025: 90th percentile AQI 561980: Median AQI 461981: Median AQI 441982: Median AQI 511983: Median AQI 491984: Median AQI 481985: Median AQI 581986: Median AQI 541987: Median AQI 511988: Median AQI 771989: Median AQI 451990: Median AQI 431991: Median AQI 391992: Median AQI 371993: Median AQI 391994: Median AQI 381995: Median AQI 371996: Median AQI 351997: Median AQI 381998: Median AQI 361999: Median AQI 622000: Median AQI 632001: Median AQI 612002: Median AQI 582003: Median AQI 582004: Median AQI 592005: Median AQI 602006: Median AQI 562007: Median AQI 592008: Median AQI 572009: Median AQI 522010: Median AQI 542011: Median AQI 532012: Median AQI 512013: Median AQI 442014: Median AQI 502015: Median AQI 462016: Median AQI 482017: Median AQI 452018: Median AQI 442019: Median AQI 442020: Median AQI 402021: Median AQI 442022: Median AQI 462023: Median AQI 502024: Median AQI 442025: Median AQI 411980198519901995200020052010201520202025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2025

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
Fine particles (PM2.5)21358%
Ozone15041%
Coarse particles (PM10)21%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025365274910000415677PM2.5
202436624911610004459122PM2.5
202336518317840005067131PM2.5
20223652231420000465984PM2.5
202136524512000004462100PM2.5
2020365288770000405588PM2.5
20193652441210000446190Ozone
201835523811610004464105PM2.5
201736522913510004561112PM2.5
201636621015240004867133PM2.5
201536421614710004661112PM2.5
201435318217100005064100PM2.5
201335722313310004460105PM2.5
201236417318371005169154PM2.5
2011361154196110005382140PM2.5
2010364136209181005480154PM2.5
200936416119940005268115PM2.5
200836510025582005782162PM2.5
20073651102153640059101195PM2.5
2006336126180282005698156PM2.5
200536593250202006093172PM2.5
200436610525380005980122PM2.5
2003364103246131105884206PM2.5
20023659122432162058119210PM2.5
200136579261214006193185PM2.5
2000366792512880063100185PM2.5
19993649920940160062115185PM2.5
19983642465944150036115192Ozone
199736525782233003890159Ozone
199636627074202003584192Ozone
199536225678244003797195Ozone
199436525873295003897192Ozone
19933652446543130039122177Ozone
19923662916690003771143Ozone
199136427077152003984172Ozone
19903652319132101043105201Ozone
198926316282172004593151Ozone
19882327976412412077172226Ozone
1987221110723270051115177Ozone
1986183885625131054143207Ozone
198518381643530058126187Ozone
19842001095427100048133182Ozone
1983206110672360049112169Ozone
198216178552071051122201Ozone
1981212138482330044108156Ozone
19801971104827120046133190Ozone

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.

Counties in North Carolina with a similar median AQI in 2025

All monitored counties in North Carolina

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem