As of 12:33 PM CDT on September 18, 2025, all 18 cities in Grayson County, TX in our database have a UV Index reading of High. The city with the highest UV Index reading right now is Sherman, TX with a reading of 6.4.
Over the next 24 hours, the highest UV Index reading in Grayson County, TX is expected to be 7.6 in Sherman between 1:00 PM - 2:00 PM CDT today.
| Range | 0 - 2 | 3 - 5 | 6 - 7 | 8 - 10 | 11+ |
|---|---|---|---|---|---|
| Color | |||||
| Risk | Low | Moderate | High | Very High | Extreme |