Sunnyvale, California, USA UV Index in September
The average UV index in Sunnyvale, California, USA in September is about 6.3 (High), peaking near 9 at midday on clear days. Fair skin (Type II) can burn in roughly 14 minutes without sunscreen. SPF 30–50 sunscreen, a hat and sunglasses are essential. Seek shade between 11am and 3pm.
What is the UV index in Sunnyvale, California, USA in September?
Average UV
6.3
High
Midday Peak
9
Clear-sky estimate
Fair Skin Burn Time
14 min
Type II, no sunscreen
How long can you stay in the sun in Sunnyvale, California, USA in September?
| Skin type | Time to first burn | With SPF 30 |
|---|---|---|
| Type 1 | 10 min | up to 240 min |
| Type 2 | 14 min | up to 240 min |
| Type 3 | 24 min | up to 240 min |
| Type 4 | 38 min | up to 240 min |
| Type 5 | 57 min | up to 240 min |
| Type 6 | 86 min | up to 240 min |
Estimates based on Sunnyvale, California, USA's latitude and typical September sun angle. Cloud cover, altitude and reflection from water or sand can raise or lower the real UV. Check the live forecast before long days outside.
Sunnyvale, California, USA UV Index by Month
When is the UV index highest and lowest in Sunnyvale, California, USA?
Highest: June (about 7). Lowest: December (about 4.6).
| Month | Average UV | Midday peak | Level | Fair skin burn |
|---|---|---|---|---|
| January | 4.8 | 6.9 | Moderate | 19 min |
| February | 5.4 | 7.7 | Moderate | 17 min |
| March | 6.1 | 8.7 | High | 15 min |
| April | 6.6 | 9.4 | High | 14 min |
| May | 6.9 | 9.9 | High | 13 min |
| June | 7 | 10 | High | 13 min |
| July | 7 | 10 | High | 13 min |
| August | 6.8 | 9.7 | High | 13 min |
| September | 6.3 | 9 | High | 14 min |
| October | 5.7 | 8.1 | Moderate | 16 min |
| November | 5 | 7.1 | Moderate | 18 min |
| December | 4.6 | 6.6 | Moderate | 20 min |
Common questions about UV in Sunnyvale, California, USA in September
Do you need sunscreen in Sunnyvale, California, USA in September?
Yes. A UV index of 6.3 is High, so use SPF 30+ on exposed skin between 10am and 4pm and reapply every two hours.
Can you tan in Sunnyvale, California, USA in September?
Yes, UV of 6.3 is strong enough to tan. Fair skin can burn in about 14 minutes, so build exposure slowly and use sunscreen.
What time of day is UV strongest in Sunnyvale, California, USA?
UV peaks around solar noon, roughly 11am to 2pm local time, when it can reach about 9 in September. Mornings and late afternoons are safest.
Is September a good month to visit Sunnyvale, California, USA for the sun?
September averages UV 6.3, compared with a yearly high of 7 in June and a low of 4.6 in December. Darker skin (Type VI) can burn in about 86 minutes at this level.