Last updated: June 2, 2025
In Koga, Japan, being aware of the UV Index is crucial for safeguarding your skin health and preventing sunburn. Understanding UV levels empowers residents and visitors alike to take necessary precautions during peak exposure hours, especially when the index reaches a high of 11 around midday. With Koga's Cfa climate, characterized by warm summers and ample sunshine, the risks associated with UV exposure can escalate quickly. By staying informed about daily UV trends, you can enjoy the beautiful outdoors while minimizing the threat of harmful rays.
The hourly UV Index reveals a dynamic rise and fall of sun intensity throughout the day. Starting at a mild 2 at 07:00, the index climbs steadily, reaching a peak of 11 at both 11:00 and 12:00, indicating a high risk of harm from unprotected sun exposure. As the afternoon sun begins to descend, the index tapers off to 9 at 13:00, then gradually decreases to 5 by 15:00. By 16:00, it drops to 3, signaling the end of peak sun strength, while cool evenings arrive with a return to 1 at both 17:00 and 18:00. Finally, at 19:00, the UV Index hits 0, marking a safe transition into the night. Stay protected during the day's brightest hours!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 2 | low | 45 min |
| 08:00 | 4 | moderate | 30 min |
| 09:00 | 7 | high | 25 min |
| 10:00 | 9 | very high | 15 min |
| 11:00 | 11 | extreme | 10 min |
| 12:00 | 11 | extreme | 10 min |
| 13:00 | 9 | very high | 15 min |
| 14:00 | 7 | high | 25 min |
| 15:00 | 5 | moderate | 30 min |
| 16:00 | 3 | moderate | 30 min |
| 17:00 | 1 | low | 45 min |
| 18:00 | 1 | low | 45 min |
| 19:00 | 0 | low | 45 min |
The UV Index exhibits notable seasonal changes throughout the year, with high-risk months primarily occurring from March to September. March marks the shift to a high category (UV Index 7), while April and May escalate to very high (UV Index 9-10), culminating in extreme exposure levels during June and July (UV Index 11). As summer transitions to fall, the UV levels gradually decline, dipping to moderate levels by November and December. Visitors and residents should take necessary precautions, especially during the peak months of June and July, where the burn time is drastically reduced to just 10 minutes. It is advisable to wear protective clothing, apply sunscreen frequently, and seek shade during these high-risk times to minimize skin damage and health risks.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sapporo UVI | 2 | 3 | 6 | 7 | 9 | 9 | 9 | 10 | 8 | 5 | 3 | 2 |
| Koga | 3 | 5 | 7 | 9 | 10 | 11 | 11 | 10 | 9 | 6 | 5 | 3 |
| Yokohama UVI | 3 | 5 | 8 | 9 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 4 |
| Tokyo UVI | 3 | 5 | 8 | 9 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 4 |
| Nagoya UVI | 4 | 6 | 8 | 10 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 3 |
| Osaka UVI | 4 | 6 | 8 | 11 | 11 | 11 | 12 | 11 | 10 | 7 | 5 | 3 |