Information

Welcome to the Wisconsin Department of Natural Resources Air Quality Monitoring Data.

General information

The statewide monitoring network is spatially distributed to provide air quality information based on geographic coverage and population density. As required by the Clean Air Act, the U.S. EPA sets National Ambient Air Quality Standards (NAAQS) for criteria pollutants:

The DNR conducts ambient air monitoring in locations directed by federal requirements to measure concentrations of these criteria pollutants for comparison to the appropriate NAAQS. For more extensive information visit DNR’s monitoring webpage.

Data validity

Data presented on this website is displayed in real time. It has not been quality assured and is therefore subject to change.
Data is quality assured within six months of collection.
Reports may not follow all rounding/truncation conventions required for comparison to the regulatory National Ambient Air Quality Standards. For example, 8-hour average ozone concentrations on this website have been rounded rather than truncated, so the values listed may be one ppb higher than their regulatory values.

Time

Data posted is the most recent available, but may appear to be older due to several factors:
- Data polls after the top of the hour and the website is updated after polling is complete.
- Data is timestamped using the beginning hour; for example, the 1-hour average for 7:00-7:59 is given the “07” hour time stamp.
- Central Standard Time is always used, so data will appear to be an additional hour behind during Daylight Savings Time.

Air Quality Index (AQI)

AQI calculations for the current day, as shown on the map and reports, use NowCast AQI calculations.^*
- NowCast AQI is a predictive model that shortens the averaging period and weights the most recent hours more heavily.
- NowCast AQI is not used for regulatory purposes, including comparison to the National Ambient Air Quality Standards.
When a new day begins, AQI values for the previous day are recalculated using the official AQI calculation; therefore, values for previous days will correspond to regulatory values.
To help users better understand current air quality conditions, 8-hour Ozone and Ozone AQI timestamps use an “hour ending” convention (e.g., the “08” hour timestamp includes the hours of 01:00 – 08:00). Conversely, for regulatory purposes, a “running forward” convention (e.g., the “08” hour timestamp includes the hours of 08:00 – 15:00) is used.

In the Reports menu under “Stations Report” the “Running Forward” Report Type may be requested.

^*On August 1, 2019 EPA completed a technical change in the background of the AirNow.gov website and updated the algorithm associated with Nowcast, which is used to estimate the AQI in real time. EPA anticipates that the revised algorithm will improve the accuracy of predictions about ozone air quality at the local level, specifically reducing the number of days when the Nowcast ozone value reported on AirNow appears to be higher than the day’s AQI forecast and/or the daily AQI. This change requires programming to apply the revised Nowcast algorithm to the DNR Air Quality web map, and that change will occur by September 1, 2019. Until this change is made there will be differences between the DNR web map and the AirNow web map.

Parameter specifications

Barometric Pressure – station conditions corrected to sea level
PM_2.5 – micrograms per cubic meter in local conditions
PM₁₀ – micrograms per cubic meter corrected to standard conditions (25 °C, 1 atmosphere pressure)
PM Coarse (particulate matter between 10 and 2.5 mm in size) – micrograms per cubic meter in local conditions
- Not expected to match the difference between PM₁₀ and PM_2.5 in many cases because the PM₁₀ concentrations have been corrected to standard conditions