As of 3:47 PM CDT on March 20, 2026, all 18 cities in Williamson County, TX in our database have a UV Index reading of High. The city with the highest UV Index reading right now is Round Rock, TX with a reading of 6.9.
Over the next 24 hours, the highest UV Index reading in Williamson County, TX is expected to be 8.2 in Round Rock between 2:00 PM - 3:00 PM CDT tomorrow.
| Range | 0 - 2 | 3 - 5 | 6 - 7 | 8 - 10 | 11+ |
|---|---|---|---|---|---|
| Color | |||||
| Risk | Low | Moderate | High | Very High | Extreme |