The Air Quality Forecast for a pollutant is different than what the current data shows. Why is that?
You are viewing the data during a small part of the day, yet values will be higher during another part of the day and that data is what the forecast is based on. This is often the case with Ozone which is a photochemical pollutant and peaks during the afternoon hours (from April through September). Both morning and evening values are likely to be low. Ozone forecasts are for the highest 8-hour period of the day. For Particle Pollution values, the running 24-hour average for several hours may be Moderate yet the block 24-hour average from midnight to midnight for that day ends up being Good. It is this block, midnight to midnight, average for which we issue the forecast. When we believe that particle levels will build in late one day and clear out early the next we will mention this in the forecast details on the Air Quality Forecasting web page.The Air Quality Trends pages have hourly and other trends for ozone and particle pollution. Finally, although we make every effort to forecast
