Nassau County, Florida air quality history

Daily Air Quality Index summaries from EPA monitors in Nassau, Florida, 1993–2020.

75%

Good days in 2019

Median daily AQI, 2019

Days above 100 in 2019

270

Days with an AQI in 2019 (of 365)

In 2019, EPA reported a daily Air Quality Index (AQI) for Nassau, Florida on 270 days. 203 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 Florida (median 40 across 39 counties), and about the same as the typical monitored U.S. county (41). The main pollutant was fine particles (PM2.5) on 270 days. Across the years with fuller monitoring, the share of Good days fell: an average of 94% in 2000–2002 versus 68% in 2017–2019.

EPA did not report an AQI for every day of 2019 here (270 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 2020; EPA's files for 2021–2025 contain no row for it, which usually means its monitors stopped reporting.

Years with fewer than 120 monitored days (1996, 1997, 1998, 1999, 2006, 2020…) 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.

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 daily AQI
90th-percentile daily AQI

Main pollutant by day, 2019

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.

Pollutant	Days as main pollutant	Share of monitored days
Fine particles (PM2.5)	270	100%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Unhealthy	Very Unhealthy	Median AQI	90th pct.	Max AQI	Main pollutant
2020	43	35	8	0	0	0	42	53	57	PM2.5
2019	270	203	67	0	0	0	41	55	74	PM2.5
2018	271	192	79	0	0	0	43	56	86	PM2.5
2017	278	160	118	0	0	0	47	62	93	PM2.5
2016	243	155	88	0	0	0	45	56	86	PM2.5
2015	344	238	106	0	0	0	43	57	71	PM2.5
2014	266	142	124	0	0	0	48	63	74	PM2.5
2013	349	234	115	0	0	0	43	58	72	PM2.5
2006	45	45	0	0	0	0	16	25	36	PM10
2005	322	313	7	1	1	0	22	38	175	PM10
2004	296	261	30	3	1	1	24	54	277	PM10
2003	353	314	36	3	0	0	20	53	140	PM10
2002	353	331	22	0	0	0	19	40	97	PM10
2001	359	328	29	2	0	0	22	44	117	PM10
2000	261	256	5	0	0	0	22	38	56	PM10
1999	60	58	2	0	0	0	24	41	54	PM10
1998	58	56	2	0	0	0	22	36	73	PM10
1997	61	59	2	0	0	0	23	33	55	PM10
1996	61	59	2	0	0	0	22	31	56	PM10
1995	61	61	0	0	0	0	21	34	50	PM10
1994	60	59	1	0	0	0	21	39	56	PM10
1993	60	59	1	0	0	0	24	36	51	PM10

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 Florida

Source: U.S. EPA AirData, “Annual AQI by County” files for 1993–2020 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem