Last updated: June 2, 2025
Understanding the UV Index is crucial for residents of Thornhill, South Africa, where sunny days are a hallmark of the climate. Being aware of UV levels helps prevent sunburn and protects skin health, making it essential for anyone spending time outdoors. With the typical UV exposure peaking during midday hours—when the index reaches up to 4—it's important to take precautions, especially during the warm months. Thornhill's Cfb climate presents its own set of challenges, with varying UV levels that can surprise even the most experienced sunbathers. Stay informed and safeguard your skin by keeping an eye on the UV Index!
The UV Index for the day unfolds a fascinating journey through the hours, starting with a maximum of 0 at 7:00 AM, indicating a safe start to the morning. As the sun ascends, the index gradually climbs to 1 by 8:00 AM and 9:00 AM, hinting at a gentle rise in UV exposure. By 10:00 AM, the UV Index reaches 2, marking the beginning of a moderate risk period. The intensity peaks at 12:00 PM with a high of 4, prompting sun safety measures to avoid overexposure. As the afternoon progresses, the index recedes slightly, stabilizing at 3 from 11:00 AM to 14:00 PM, before tapering off to 1 by 16:00 PM, and finally returning to 0 by the evening. This daily UV cycle highlights the importance of sun safety, especially during midday hours when UV radiation is strongest.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 0 | low | 45 min |
| 08:00 | 1 | low | 45 min |
| 09:00 | 1 | low | 45 min |
| 10:00 | 2 | low | 45 min |
| 11:00 | 3 | moderate | 30 min |
| 12:00 | 4 | moderate | 30 min |
| 13:00 | 3 | moderate | 30 min |
| 14:00 | 3 | moderate | 30 min |
| 15:00 | 2 | low | 45 min |
| 16:00 | 1 | low | 45 min |
| 17:00 | 1 | low | 45 min |
| 18:00 | 0 | low | 45 min |
| 19:00 | 0 | low | 45 min |
Throughout the year, UV Index levels exhibit significant seasonal fluctuations, with extreme UV exposure occurring from January to March, where the index peaks at 14 in January and December. Visitors and residents should exercise caution during these months, as the burn time is as little as 10 minutes. The UV Index remains high in April, with a value of 8, before dropping to a moderate level of 5 in May and 4 from June to July. As summer wanes into August, the UV Index rises again to 6, prompting a high risk label, before returning to very high levels of 8 in September. The year closes with another spike in UV exposure, notably in October and November, where the index reaches 12, emphasizing the need for protective measures during these extreme periods. To safeguard against UV exposure, it's advisable for everyone to apply sunscreen and wear protective clothing, especially during the high-risk months.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cape Town UVI | 14 | 13 | 11 | 8 | 5 | 3 | 4 | 6 | 9 | 11 | 12 | 14 |
| Thornhill | 14 | 13 | 11 | 8 | 5 | 4 | 4 | 6 | 8 | 11 | 12 | 14 |
| Durban UVI | 14 | 13 | 12 | 9 | 6 | 4 | 5 | 7 | 9 | 11 | 13 | 15 |
| Johannesburg UVI | 15 | 15 | 13 | 10 | 7 | 6 | 6 | 8 | 11 | 12 | 14 | 16 |
| Pretoria UVI | 16 | 15 | 13 | 10 | 7 | 6 | 6 | 9 | 11 | 13 | 14 | 16 |
| Soweto UVI | 16 | 15 | 13 | 11 | 7 | 6 | 6 | 8 | 11 | 13 | 15 | 16 |