A morning outdoor plan and a decision about going out right now may draw on different air-quality information. On AirNow, a forecast and the NowCast share an index scale but do not describe the same time window. Read the product label before comparing numbers, then use the agency’s guidance for the pollutant and people concerned. A city-level reading is not a personal exposure measurement or a clinical clearance.
| Product | Question it supports | Context to retain |
|---|---|---|
| AQI forecast | What conditions are predicted for the relevant day? | Issue/valid time, area, pollutant and discussion |
| NowCast AQI | What does the latest available current-air calculation show? | Latest hour/area/pollutant, not an assumed instantaneous personal reading |
The forecast is a planning expectation
AirNow describes an AQI forecast as a prediction of the day’s air quality, generally focused on the next day and issued by state/local forecasters. It notes that conditions can change and recommends checking forecasts each day. The forecast discussion, where provided, may help explain when pollution is expected to be higher or lower.
For an original plan note, retain the forecast’s source, area, issue/valid time and pollutant information. A screenshot without its date can turn yesterday’s expectation into an apparent statement about today. Keep the forecast attached to the actual day you are planning.
The NowCast is current information with an averaging method
AirNow says its NowCast relates monitor readings to the AQI for ozone or particle pollution. It uses multiple hours of past data to describe the most current hour available, with averaging responsive to changing conditions. It is not simply a promise of an instantaneous reading at your exact location.
Compare the questions, not just the colors
Imagine a purely hypothetical situation in which a day’s forecast and the current display differ. First check that both refer to the same area and relevant day, then identify whether you are comparing a forecast with a NowCast. Do not silently relabel one as a failed measurement or declare the whole day suitable from a single screen. No real local readings or outdoor test are reported here.
Keep the displayed category and the linked agency activity guidance with your note. AirNow publishes separate particle-pollution and ozone activity guides. Follow the applicable official advice and any individual care plan from your clinician; this article supplies no personalized activity threshold or treatment instruction.
Leave room to change the plan
Before paying for an outdoor booking, understand its actual change/cancellation terms separately from the air-quality information. Recheck relevant current information as the activity approaches and use the responsible agency’s guidance when choosing an alternative. A saved reading supports an informed plan only when its time and limitations remain visible.
Sources & further reading
Published sources for the details and examples discussed in this story.
