The index is divided into six categories, each corresponding to a different level of health concern. An AQI of over 100 triggers an alert for vulnerable groups.

More: Air Quality Index (AQI) Basics What do the numbers mean? An AQI level of 50 or below represents good air quality, while an AQI value of more than 300 represents hazardous air quality.

Ultraviolet radiation, and thus UV index numbers, are higher when the sun is at a higher angle in the sky. Outside of the tropics, this means the UV index is highest during midday in the summer.

The Consumer Price Index in June rose 2.7% on an annual basis, a sign inflation around the U.S. is creeping up after declining earlier this year. By the numbers ...

The UV index measures the strength of the sun's ultraviolet (UV) radiation. The index ranges from 0 to 11, with higher numbers indicating greater risk of sunburn and skin damage.