The maps show forecast ground-level hourly and 8-hourly average Ozone (O₃) concentrations (ppb) for the northeast US, based on a 12 km grid, normally updated daily around 1830 UTC.   The maps are an experimental product of the Air Quality Forecast System by the National Weather Service.  These products are intended to provide guidance to local and state air quality forecasters, and provide information for people at risk, but do not constitute an air quality warning or alert.  Please refer to your current air quality forecast which is available at the EPA AIRNow web site.