Last updated: March 2, 2024
The weather in Grass Valley, United States, during September is characterized by an average temperature of 21°C (70°F). Highs can soar to 37°C (99°F), while lows may dip to 8°C (47°F). Typically, the humidity level in Grass Valley throughout September hovers around 44%.
Minimum temperature
Average temperature
Maximum temperature
Humidity
In September, Grass Valley averages 23 mm (0.9 inches) of rainfall, typically over the course of 2 rainy days. The month enjoys an average of 12 hours 23 minutes of daylight, with the sun shining for approximately 10 hours 29 minutes each day. Additionally, there is a 84% probability of sunny days during this period.
Precipitation
Rainy days
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Chance of sun
In September, the UV Index in Grass Valley reaches a maximum of 9, indicating a level of VeryHigh exposure. The most intense UV radiation typically occurs between 13:00 and 15:00, during which unprotected skin may burn in as little as 15 minutes.
| 07:00 | 08:00 | 09:00 | 10:00 | 11:00 | 12:00 | 13:00 | 14:00 | 15:00 | 16:00 | 17:00 | 18:00 | 19:00 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UVI | 1 | 1 | 2 | 4 | 6 | 8 | 9 | 8 | 6 | 4 | 2 | 1 | 1 |
| Exposure | Low | Moderate | High | VeryHigh | High | Moderate | Low | ||||||
| Time to burn | 45 min | 30 min | 25 min | 15 min | 25 min | 30 min | 45 min | ||||||