How accurate is the forecast?

We compare every forecast against what the day actually turned out to be. These figures update themselves; we do not pick the days that flatter us.

Not enough data yet. A forecast needs a few days before there is an actual reading to compare it against.

Method: a day's forecast index is compared against that day's 24-hour mean, which is how DOE defines the index. Forecast from the Open-Meteo (CAMS) model; actuals from the Department of Environment.