UV Index chart card

Who it’s for

Public health managers, outdoor venue operators, and school safety coordinators ask “how has the UV index changed over the selected period, and how does today’s exposure risk compare to the same period last week?” They want the current index, the daily curve, and the period-over-period shift in one card.

What it does

A sensor averaging 6 this week versus 3 last week shows an orange value — High — with a +100% delta and a +3 absolute change, plus a chart of readings over the selected window.

• Large current UV index value color-coded across five bands from Low to Extreme
• Delta percentage and absolute delta comparing the current period to the previous one
• Time-series chart of UV index readings averaged per interval
• Shows one sensor’s data; it does not compare multiple sensors

How to set up

Data keys

Key	Role	Type	Description
uv	Chart series	Timeseries	UV index (dimensionless); drives the chart and all derived overlays
Latest	Latest value	Timeseries	The headline figure above the chart. Its own color ranges are where the band colors are edited
Delta percent	Percentage change	Timeseries	Change against the previous period, as a percentage
Delta absolute	Absolute change	Timeseries	Change against the previous period, in the key’s own unit

The widget ships with a simulated function datasource key labeled UV Index, so it draws random values until you point the datasource at a device and rename the key.

To point it at your own device: open the dashboard in edit mode, open the widget’s Datasources, pick the entity or entity alias, and replace the function key with the key your device reports.

If the key has never reported for the selected time window, the chart is empty and all overlays show no data.

Value ranges

Range	Level	Color
0–2	Low	Green
2–5	Moderate	Orange
5–7	High	Orange
7–10	Very High	Red-Orange
10+	Extreme	Red

How to customize

• To use your own UV thresholds — edit the color ranges on the Latest data key; adjust the five default bands to match your public health advisory thresholds.
• To change the comparison period — adjust the Time window on the dashboard; the delta automatically compares to the equivalent preceding period.
• To hide or show the chart — toggle Show chart in the widget settings.
• To change the chart line color — set Chart color.
• To hide the entity name subtitle or the timestamp — turn off Show subtitle or Show date.
• To match your dashboard’s fonts — set the font options under each data key’s appearance settings.

Tips

• A week-over-week positive delta in spring is expected as solar angle increases; a sudden spike mid-summer without a corresponding rise in solar radiation may indicate ozone depletion or unusual atmospheric conditions worth flagging.
• The UV index peaks at solar noon and drops to zero at night — a chart that shows anything other than a clean daily bell curve may indicate sensor fouling, incorrect orientation, or shading.
• Pair with a solar radiation chart card: high UV with relatively lower irradiance can occur under scattered cloud, which is a less intuitive condition but still poses a sunburn risk.