What you need
- Multimeter for macOS 13 or later, $19.99 once.
- Your latitude and longitude.
Set it up
- Find your latitude and longitude. Open-Meteo’s place search gives them for any town (the first result’s
latitudeandlongitude):Terminalcurl -s 'https://geocoding-api.open-meteo.com/v1/search?name=Plano&count=1' - Add a Web Address meter with this address and the key path
current.uv_index:Web addresshttps://api.open-meteo.com/v1/forecast?latitude=33.02&longitude=-96.70¤t=uv_index - Refresh every 15 minutes. Range 0 to 11; alerts on High values at 6 and 8.
Multimeter settings
In Customize This Meter… (from the meter’s menu):
| Setting | Value |
|---|---|
| Source | Web Address |
| Web address | https://api.open-meteo.com/v1/forecast?latitude=LAT&longitude=LON¤t=uv_index |
| Key path | current.uv_index |
| Refresh every | 15 minutes |
| Range | 0 to 11 |
| Alerts | High values: warning 6, critical 8 |
| Label | UV |
| Face | Signal Bars, Ring or Traffic Light |
Tested: Run on October 29, 2026 at 11:45 in Plano, Texas: 3.65.
More on this source, including every format it reads, in the Web Address guide.
Limits
- Open-Meteo allows up to 10,000 calls a day for non-commercial use without a key; one meter every 15 minutes uses 96. Its models update about every hour.
Variations
Today’s peak
&daily=uv_index_max&timezone=auto&forecast_days=1, key path daily.uv_index_max.0.
Troubleshooting
| Symptom | Cause | Fix |
|---|---|---|
| No number found in the response | The key path doesn’t match the reply. | Run curl -s with the address and read the JSON. Dots walk into objects, numbers pick array items (items.0.count). |
| Couldn’t reach the address | No network, a typo in the host, or the service is down. | Open the address in your browser. Multimeter tries again at the next refresh. |
Questions
What levels need sun protection?
The WHO scale: 3 to 5 moderate, 6 to 7 high, 8 to 10 very high, 11 and up extreme. Protection is advised from 3.