Power County, Idaho air quality history

Daily Air Quality Index summaries from EPA monitors in Power, Idaho, 1996–2010.

92%

Good days in 2009

Median daily AQI, 2009

Days above 100 in 2009

194

Days with an AQI in 2009 (of 365)

In 2009, EPA reported a daily Air Quality Index (AQI) for Power, Idaho on 194 days. 179 of those days (92%) were in the Good range, and the median daily AQI was 19. That median is lower than the typical monitored county in Idaho (median 30.5 across 16 counties), and lower than the typical monitored U.S. county (41). The main pollutant was coarse particles (PM10) on 124 days. Across the years with fuller monitoring, the share of Good days rose: an average of 36% in 1997–1999 versus 80% in 2007–2009.

EPA did not report an AQI for every day of 2009 here (194 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 2010; EPA's files for 2011–2025 contain no row for it, which usually means its monitors stopped reporting.

Years with fewer than 120 monitored days (1996, 2010) 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, 2009

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
Coarse particles (PM10)	124	64%
Fine particles (PM2.5)	70	36%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Unhealthy	Very Unhealthy	Hazardous	Median AQI	90th pct.	Max AQI	Main pollutant
2010	4	4	0	0	0	0	0	20	24	24	PM10
2009	194	179	15	0	0	0	0	19	44	84	PM10
2008	296	222	71	2	1	0	0	36	58	168	PM2.5
2007	360	257	103	0	0	0	0	34	59	91	PM2.5
2006	362	208	152	2	0	0	0	46	64	146	PM2.5
2005	363	183	176	2	2	0	0	50	63	170	PM2.5
2004	365	190	169	5	1	0	0	49	65	172	PM2.5
2003	356	205	151	0	0	0	0	46	62	90	PM2.5
2002	345	168	174	3	0	0	0	51	64	130	PM2.5
2001	354	78	271	4	1	0	0	60	79	164	PM2.5
2000	341	41	237	39	18	6	0	70	132	241	PM2.5
1999	327	28	184	60	48	6	1	84	162	488	PM2.5
1998	136	67	59	8	0	2	0	52	95	243	PM10
1997	352	172	151	23	5	1	0	51	91	277	PM10
1996	84	22	40	16	4	1	1	68	137	319	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 Idaho

Source: U.S. EPA AirData, “Annual AQI by County” files for 1996–2010 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem