Last updated: June 2, 2025
Understanding the UV Index is crucial for residents of Great Falls, Montana, where the sun's rays can be deceptively strong, even on seemingly mild days. As part of the Cfa climate zone, Great Falls experiences varied weather, but the potential for high UV exposure during peak hours—especially around noon—makes knowing these levels essential for sunburn prevention and maintaining long-term skin health. With UV Index values peaking at 10—indicating a very high risk—awareness helps you take proactive measures to safeguard against harmful effects, ensuring enjoyable days outdoors without compromising your well-being.
As the sun rises, the UV Index begins its ascent, peaking at an invigorating 10 by 1:00 PM. Early morning, from 7:00 AM to 8:00 AM, sees a mild 1 to 2, making it a perfect time for a leisurely stroll. By 9:00 AM, the UV Index reaches 3, signaling a need for some sun protection. The real intensity kicks in around 11:00 AM, hitting 8, and just after noon, it soars to its daily maximum of 9. The afternoon hours see a slight decline, with values tapering from 9 at 2:00 PM to 6 by 4:00 PM. As daylight wanes, the UV Index gently drops to 1 by 7:00 PM, wrapping up a day of vibrant sunlight but reminding us to stay vigilant during those peak hours. Remember to reapply sunscreen and seek shade to keep safe while enjoying those sunny moments!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 2 | low | 45 min |
| 09:00 | 3 | moderate | 30 min |
| 10:00 | 6 | high | 25 min |
| 11:00 | 8 | very high | 15 min |
| 12:00 | 9 | very high | 15 min |
| 13:00 | 10 | very high | 15 min |
| 14:00 | 9 | very high | 15 min |
| 15:00 | 8 | very high | 15 min |
| 16:00 | 6 | high | 25 min |
| 17:00 | 4 | moderate | 30 min |
| 18:00 | 2 | low | 45 min |
| 19:00 | 1 | low | 45 min |
Throughout the year, the UV Index demonstrates significant seasonal changes, highlighting the need for awareness regarding sun exposure. From January to February, UV levels are moderate (index 3-5), with a burn time of 30 minutes. As spring arrives in March, the index rises to 7, indicating high exposure risk with a reduced burn time of 25 minutes. The peak risk occurs from April through August, where the index reaches its highest levels (9-10) and burn times drop to just 15 minutes, categorizing these months as very high risk. In September and October, the UV index remains significant but decreases to high levels (7-8) with a burn time of 25 minutes. November and December return to moderate levels (index 3-5) with a burn time of 30 minutes. For visitors and residents alike, it is crucial to take protective measures, especially during the high-risk months from April to August, by using sunscreen, wearing protective clothing, and seeking shade during peak sunlight hours.
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 |
| Great Falls | 3 | 5 | 7 | 9 | 10 | 10 | 10 | 9 | 8 | 7 | 5 | 3 |
| Los Angeles UVI | 4 | 6 | 8 | 9 | 10 | 11 | 11 | 10 | 10 | 7 | 5 | 4 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |