Last updated: June 24, 2025
In September, the average temperature in Walnut, United States is a pleasant 20°C (69°F). However, you can expect a minimum of 3°C (39°F) and a maximum of 35°C (95°F), providing a diverse climate experience. Rainfall averages around 110 mm (4.3 in) over approximately 10 days, contributing to a high average humidity of 80%. Whether you’re exploring the outdoors or enjoying indoor activities, be prepared for a range of weather conditions!
In September in Walnut, the average temperature is 20°C (69°F), with maximums reaching 35°C (95°F) and minimums dropping as low as 3°C (39°F). This diverse range of temperatures makes it a perfect time for travelers to enjoy both warm days and cooler evenings.
In Walnut in September, the precipitation amount is 110 mm (4.3 in) over a period of 10 days.
In Walnut in September, humidity is 80%. With an average temperature of 20°C (69°F), this humidity feels like a warm blanket enveloping you, making every step slightly more challenging as you navigate the air that clings to your skin, often leaving you longing for a cool breeze while exploring the sights.
In Walnut in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in Walnut.
UV Risk Categories
Weather in Walnut varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Walnut, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -4°C (25°F) | 58 mm (2.3 inches) | 82% | moderate |
| February Weather | -3°C (27°F) | 62 mm (2.5 inches) | 83% | moderate |
| March Weather | 4°C (40°F) | 94 mm (3.7 inches) | 84% | high |
| April Weather | 10°C (49°F) | 114 mm (4.5 inches) | 85% | very high |
| May Weather | 17°C (62°F) | 173 mm (6.8 inches) | 79% | very high |
| June Weather | 23°C (73°F) | 146 mm (5.7 inches) | 82% | very high |
| July Weather | 24°C (76°F) | 100 mm (3.9 inches) | 80% | very high |
| August Weather | 23°C (74°F) | 68 mm (2.7 inches) | 81% | very high |
| September Weather | 20°C (69°F) | 110 mm (4.3 inches) | 80% | very high |
| October Weather | 12°C (55°F) | 127 mm (5.0 inches) | 82% | high |
| November Weather | 4°C (39°F) | 55 mm (2.2 inches) | 88% | moderate |
| December Weather | 0°C (33°F) | 49 mm (1.9 inches) | 84% | low |