As of 12:10 AM EDT on September 3, 2025, all 17 cities in Mercer County, NJ in our database have a UV Index reading of 0, indicating no radiation from the sun.
Over the next 24 hours, the highest UV Index reading in Mercer County, NJ is expected to be 7 in Hopewell between 1:00 PM - 2:00 PM EDT today.
| Range | 0 - 2 | 3 - 5 | 6 - 7 | 8 - 10 | 11+ |
|---|---|---|---|---|---|
| Color | |||||
| Risk | Low | Moderate | High | Very High | Extreme |