UV Index
UV Index
Today's UV index in Boulder, United States 
will be up to 11.8, indicating a extreme level of sun exposure for the average person. Check our tips for today to make sure you're safe in the sun.
Last checked: 2025-06-22
UV index at 11.8 in Boulder means extreme risk: limit outdoor time especially from 10 a.m. to 4 p.m., actively seek shade, wear protective clothing, broad-brimmed hat, apply SPF 30+ sunscreen every 2 hours, and wear UV-blocking sunglasses. Watch for bright surfaces like water and snow increasing UV exposure.
Boulder's UV index can be quite high, especially in summer, often reaching levels of 7 to 9, which means strong sun exposure. In winter, the UV index drops significantly, sometimes below 2.
Boulder experiences four distinct seasons. Summers are warm and sunny, while winters are cold with occasional snow. Springs and autumns are mild, with moderate temperatures and changing leaves in fall.
Compared to nearby Denver, Boulder is slightly cooler due to its higher elevation. The region has more sunshine than many other parts of Colorado. Neighboring states like Wyoming and Nebraska generally have lower UV indexes and cooler temperatures.
See the UV index hour by hour for Boulder, along with the temperature and how cloudy it is. If the UV level is higher than moderate, it's best to avoid direct sunlight.