Last updated: August 1, 2025
Understanding the UV Index is crucial for residents and visitors in Hatsudai, Japan, as it empowers individuals to make informed decisions about sun exposure. With peaks reaching 11 between 11:00 AM and 12:00 PM, the risk of sunburn increases significantly, making awareness essential for maintaining skin health. Hatsudai's Cfa climate means warm summers and varying UV levels throughout the day, underscoring the need for protective measures during peak sunlight hours. By monitoring local UV levels, you can better protect yourself and your loved ones from harmful UV rays while enjoying the beautiful outdoors.
As the sun rises, the UV Index begins its climb, starting at a modest 2 at 7:00 AM. By 8:00 AM, it gains momentum, reaching 4, but the real peak arrives between 10:00 AM and 12:00 PM, where it soars to a striking 11. This is the time to seek shade or wear protective gear, as the sun's rays are at their harshest. After noon, the intensity wanes slightly with readings of 10 at 1:00 PM and gently dropping to 8 by 2:00 PM. As the afternoon turns to evening, the index cools down to 5 at 3:00 PM, before dipping to 3 by 4:00 PM, and ultimately settling at 1 by 6:00 PM. By sunset, the danger fades, leaving a 0 UV reading at 7:00 PM. Keep an eye on the UV Index to enjoy the sun safely!
| 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 | 2 | low | 45 min |
| 17:00 | 1 | low | 45 min |
| 18:00 | 1 | low | 45 min |
| 19:00 | 0 | low | 45 min |
As the seasons change, the UV Index fluctuates significantly, influencing the risk of sun exposure throughout the year. January and February start with a moderate UV Index of 3 and 5, allowing for a burn time of 30 minutes. However, by March, the UV Index jumps to 8, which is categorized as very high, reducing safe exposure to just 15 minutes. The peak months for UV radiation are May through August, where the Index reaches an extreme level of 11, necessitating a mere 10 minutes of exposure before risking sunburn. September begins a gradual decline to a very high index of 10, while October and onward return to moderate levels. Visitors and residents should be particularly cautious from March to August—wearing protective clothing, applying sunscreen, and seeking shade to minimize UV damage during these high-risk months.
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 |
| Hatsudai | 3 | 5 | 8 | 9 | 11 | 11 | 11 | 11 | 10 | 7 | 5 | 4 |
| 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 |