Guide to the map and measurements
Use this page when you want to understand what the map is showing, change how monitoring locations are displayed, or interpret the information inside a monitor popup.
Three things to know first
Start with color
Particulate-matter monitor colors represent the current PM2.5 Air Quality Index. Green is lower AQI; warmer and darker colors indicate increasing health concern.
Click a marker
Select a monitoring location to see its current value and recent history. PM-monitor popups include an AQI gauge and a 72-hour PM2.5 chart.
Use the legend
Turn monitoring layers on or off, show PM monitor types with different shapes, or color weather stations by temperature.
Choose how the map is displayed
Particulate-matter monitors
By default, all PM monitors use the same circle shape. This keeps the map visually simple while AQI color remains the primary signal.
Turn on Show PM monitor types in the legend when you want the marker shape to identify the instrument network. PurpleAir locations become triangles and QuantAQ locations become diamonds. Additional monitor types can be given their own shapes as they are added.
Weather stations
Weather stations appear as light-gray squares with wind arrows by default so they do not compete visually with AQI information. The arrow shows wind direction, and longer arrows indicate stronger wind.
Turn on Show temperature to color the square by current temperature; the wind arrow remains visible. Click a weather station for temperature, humidity, pressure, wind, and 24-hour summary information.
Reading AQI colors
The Air Quality Index (AQI) translates pollutant concentrations into a common color-coded scale. PM monitor marker colors and the gauge inside each PM popup use the same categories.
For background on particulate matter, local sources, health context, and ways to reduce exposure, visit Learn.
What is inside a popup?
PM monitors
The semicircular gauge shows the most recent AQI category and PM2.5 concentration. The chart below it shows PM2.5 measurements over the previous 72 hours so you can see whether current conditions are typical, rising, falling, or part of a short event.
Weather stations
Weather popups summarize the latest temperature, humidity, pressure, and wind information, along with minimum, maximum, and average values from the recent period when those data are available.
On phones, the popup opens as a full-screen view with a clearly marked Close button. On larger screens, it remains a compact popup over the map.