The summary shows the useful coverage per variable in the selected range: measurements with a value that passed quality control, counted against each sensor's own sampling cadence.
The map adapts its granularity to the range length: daily up to 120 days, weekly up to about 2 years, monthly beyond that. Each aggregated cell shows its worst day — a single day without data paints its whole week/month red, so gaps are exaggerated, never hidden.
To locate a gap exactly, narrow the date range over the red zone: the map switches back to weekly and then daily detail.
Results are computed from the mean climatological year: the average of all valid historical data for each calendar instant (not a TMY, not an observed year).
Results are computed from the mean climatological year: the average of all valid historical data for each calendar instant (not a TMY, not an observed year).
Results are computed from the observed station data for the selected year (not from the mean climatological year).