Good
PM2.5 in Idaho is currently 1.1 µg/m³, within the WHO guideline.
What should you do at this air quality level?
- The air is clean. Enjoy exercise and outdoor activities.
- A good time to open the windows and air out your home.
Pollutants compared with WHO guidelines
The vertical line marks the World Health Organization guideline (WHO, 2021). Figures are instantaneous concentrations from the OpenWeather model and are for reference only; for official monitoring and wildfire smoke forecasts, see AirNow.gov (US EPA) and your state air agency.
Air quality ranking by state
Most polluted firstWhat is the AQI?
The AQI (Air Quality Index) turns pollutant concentrations into an easy-to-read 0–500 scale: the higher the number, the more polluted the air. This page calculates the AQI on the US Environmental Protection Agency scale (US EPA, 2024 update) from PM2.5, the pollutant with the greatest health impact, the same scale used by AirNow.gov.
Fine particles tend to build up on calm mornings and evenings, during temperature inversions in winter valleys and during heavy traffic. In summer and fall, smoke from wildfires — sometimes hundreds of miles away — can push the AQI into unhealthy levels. Ground-level ozone peaks on hot, sunny afternoons. After rain or a cold front, the air is usually noticeably cleaner.