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Improving NowCasts and 24-hour rolling means

Available starting 2026-10-12

The dataVersion parameter and data version v2026-11-10 are available starting 2026-10-12.

We are improving how NowCasts and 24-hour rolling means are calculated.

Schedule

We are releasing the improved aggregates in stages. If you want to see them early, you can request them from the API during the preview: use the dataVersion parameter.

Stage Date API Dashboard
Preview 2026-10-12 Request the improved aggregates with "dataVersion": "v2026-11-10". Requests without dataVersion are unchanged Unchanged
Dashboard 2026-10-26 Unchanged Shows the improved aggregates
Default 2026-11-10 Requests without dataVersion get the improved aggregates. To delay your transition, send "dataVersion": "legacy" Shows the improved aggregates
Retirement 2027-01-11 legacy is retired. Requests for it get the improved aggregates Shows the improved aggregates

What is improving

Today, a NowCast or 24-hour rolling mean is calculated over every hour in its window, including hours that failed quality control. In addition, a 24-hour rolling mean is reported as valid even when the device reported for only part of the day.

With the improved aggregates:

  • They cover your full history. We are recalculating NowCasts and 24-hour rolling means across all historical data, so a historical request with v2026-11-10 returns improved aggregates for any period, not just data from 2026-10-12 onward.
  • Hours that failed quality control are left out whenever enough good hours remain. The value is calculated from the good hours, the metric reports valid, and the new warning flag QC.W.FLT.001 tells you some hours were filtered out.
  • 24-hour rolling means need at least 18 hours to be valid. If the device reported fewer than 18 of the 24 hours, the metric reports invalid with flag QC.I.AGG.001. If it reported enough hours but fewer than 18 have a calibrated value, it reports invalid with QC.I.AGG.002.

What does not change

  • Only NowCasts, 24-hour rolling means and their AQIs change. Individual measurements, 1-hour means and daily means keep their values.
  • The shape of a response does not change. The same metrics come back with the same attributes, and a CSV or Parquet file has the same columns.
  • raw and status do not change.
  • Reference sites do not change.

How to try it

The API now has data versions. The improved aggregates are data version v2026-11-10, and today's values are legacy. To try the new version, add "dataVersion": "v2026-11-10" to a recent or historical measurements request. We recommend also requesting qcAssessment and qcFlags so you can see which periods are incomplete.

Do you need to do anything?

  • No. Your existing API calls will start returning the improved aggregates on 2026-11-10.
  • If you need more time, add "dataVersion": "legacy" to your requests before 2026-11-10. That gives you until 2027-01-11 to adjust.
  • To prepare early, try v2026-11-10 now and compare it with your current results.

We would love your feedback during the preview. Write to support@clarity.io.

Together with the preview on 2026-10-12, we are making the following unversioned changes. They apply regardless of the dataVersion you request, including legacy, and they apply to history as well as new data.

  • Reference-site 24-hour rolling means are null when fewer than 18 of the 24 hours reported. Reference-site data never carries QC values, so the flags QC.I.AGG.001 and QC.I.AGG.002 do not appear on them.
  • QC and status on AQIs with no value. Some AQIs with a null value were returned with a QC assessment, QC flags or a status, and the recent and historical endpoints did not always agree. These are now more correct and consistent across both.
  • Rolling means and NowCasts after a data gap. Some values in the hours after a gap in a device's or reference site's data were missing from history. They are now filled in.