What is the “best index” on a weather monitor?

There are a few possibilities depending on what you’re interested in:

• For general outdoor comfort:
  The Heat Index (combining temperature and humidity) or Wind Chill Index (for cold, windy conditions) are the main comfort indicators.
• For storm or severe weather awareness:
  The Barometric Pressure Trend and Humidity are key — a falling pressure often indicates approaching bad weather.
• For astronomical or radio work:
  The Dew Point, Humidity, and Cloud Cover Index (if your system includes it) are most useful. Dew point near air temperature means likely condensation — bad for optics and radio gear.
• For air quality and health monitoring:
  The AQI (Air Quality Index) is most important if your weather monitor tracks pollutants or particulates.