Last updated: July 2, 2025
Understanding the UV Index is crucial for residents and visitors in Grand Junction, given the area's Dfb climate which brings a unique combination of sunny days and higher altitudes, elevating UV exposure risks. Monitoring UV levels can help prevent sunburn, protect skin health, and reduce long-term risks of skin damage. With peak UV readings in the afternoon soaring to levels as high as 12, it's vital to stay informed and take necessary precautions during the sunniest hours to enjoy the beautiful outdoor lifestyle of Grand Junction safely.
The UV Index rises sharply as the day unfolds, starting gently at 1 by 7:00 AM. As the sun climbs higher, it reaches 2 by 8:00 AM and then jumps to 4 by 9:00 AM. The intensity peaks around midday, hitting a striking 11 at 12:00 PM, followed closely by a maximum of 12 from 1:00 PM to 2:00 PM. In the afternoon, the index begins to decline, dropping to 10 by 3:00 PM and further down to 5 by 5:00 PM. As daylight wanes, the value lowers to 1 by 7:00 PM, indicating a rapid decrease in UV exposure. This cyclical pattern highlights the importance of sun protection during peak hours, especially between 11:00 AM and 2:00 PM when the UV Index is highest.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 2 | low | 45 min |
| 09:00 | 4 | moderate | 30 min |
| 10:00 | 6 | high | 25 min |
| 11:00 | 9 | very high | 15 min |
| 12:00 | 11 | extreme | 10 min |
| 13:00 | 12 | extreme | 10 min |
| 14:00 | 12 | extreme | 10 min |
| 15:00 | 10 | very high | 15 min |
| 16:00 | 7 | high | 25 min |
| 17:00 | 5 | moderate | 30 min |
| 18:00 | 2 | low | 45 min |
| 19:00 | 1 | low | 45 min |
Throughout the year, the UV Index experiences significant seasonal changes, with the highest levels occurring in the summer months. From May to August, the UV Index ranges from 11 to 12, classifying these months as having an extreme exposure category, meaning the risk of harm from unprotected sun exposure is very high. Specifically, March to September are identified as high-risk months, where the burn time drastically decreases to as little as 10 minutes in peak summer. Visitors and residents are strongly advised to take precautions during these months, such as wearing protective clothing, applying broad-spectrum sunscreen, and seeking shade to minimize UV exposure and protect skin health. As the year progresses towards fall and winter, the UV Index decreases, with January, November, and December classified as moderate, allowing for safer sun exposure, though caution is still recommended.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chicago UVI | 3 | 4 | 6 | 8 | 9 | 10 | 10 | 9 | 8 | 6 | 4 | 2 |
| Brooklyn UVI | 3 | 5 | 6 | 8 | 10 | 10 | 9 | 9 | 8 | 6 | 4 | 2 |
| New York City UVI | 3 | 5 | 6 | 8 | 10 | 10 | 9 | 9 | 8 | 6 | 4 | 2 |
| Los Angeles UVI | 4 | 6 | 8 | 9 | 10 | 11 | 11 | 10 | 10 | 7 | 5 | 4 |
| Grand Junction | 4 | 7 | 8 | 10 | 11 | 12 | 12 | 11 | 10 | 7 | 5 | 4 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |