Last updated: June 24, 2025
The average temperature in Fountain Valley, United States during September is a pleasant 22°C (72°F). Expect minimums around 15°C (58°F) and soaring highs of up to 38°C (102°F). With a meager 3 mm (0.1 in) of precipitation spread across 0 days, the weather is likely to be quite dry. Additionally, you can anticipate an average humidity of 68%, creating a warm and comfortable atmosphere.
In September, in Fountain Valley, the average temperature is 22°C (72°F). Maximums can reach 38°C (102°F), while minimums can drop as low as 15°C (58°F). This makes September a great time to visit Fountain Valley, offering warm days ideal for outdoor activities and cooler nights perfect for comfortable evenings.
In Fountain Valley in September, the precipitation amount is 3 mm (0.1 in) during a total of 0 days.
In Fountain Valley in September humidity is 68%. With an average temperature of 22°C (72°F), this humidity feels like a warm embrace, slightly stifling but still manageable for traveling, creating an atmosphere that encourages leisurely outdoor activities while prompting occasional breaks for refreshment.
In Fountain Valley in September, the maximum UV index reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, you can check the Hourly UV Index in Fountain Valley.
UV Risk Categories
Weather in Fountain Valley varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Fountain Valley, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | 14°C (57°F) | 65 mm (2.5 inches) | 74% | moderate |
| February Weather | 14°C (58°F) | 52 mm (2.0 inches) | 79% | high |
| March Weather | 15°C (60°F) | 55 mm (2.2 inches) | 75% | very high |
| April Weather | 17°C (63°F) | 23 mm (0.9 inches) | 70% | very high |
| May Weather | 18°C (64°F) | 12 mm (0.5 inches) | 70% | very high |
| June Weather | 20°C (68°F) | 4 mm (0.2 inches) | 72% | extreme |
| July Weather | 22°C (72°F) | 3 mm (0.1 inches) | 73% | extreme |
| August Weather | 23°C (73°F) | 2 mm (0.1 inches) | 69% | very high |
| September Weather | 22°C (72°F) | 3 mm (0.1 inches) | 68% | very high |
| October Weather | 20°C (69°F) | 9 mm (0.4 inches) | 67% | high |
| November Weather | 17°C (63°F) | 18 mm (0.7 inches) | 68% | moderate |
| December Weather | 14°C (58°F) | 68 mm (2.7 inches) | 71% | moderate |