September weather forecast
Fullerton, CA

September receives residual summer warmth as recorded with a high temperature of 82.2°F (27.9°C), although a downward trend from August. There is no drastic increase in the amount of rainfall which stands at 0.2" (5mm), reaffirming the continuous dry spell. This month offers an ideal blend of summer sun and gentle breezes, making it a delightful month for a visit. September proves to be a delightful transition from the peak summer towards cooler months, with a gradual decrease in daylight hours. Get ready for fuller cloud coverage and a mild drop in temperature as we head towards fall.

Temperature

The advent of September in Fullerton, California, observes an average high-temperature of a still warm 82.2°F (27.9°C), nearly identical to August's 83.5°F (28.6°C). During the month of September, Fullerton experiences a steady low-temperature average of 64.8°F (18.2°C).

Heat index

Throughout September, the heat index is appraised at 84.2°F (29°C). With unrelenting exposure and activity, one might experience exhaustion, leading to potential heat cramps.
One should be cognizant that the heat index values are tailored for shaded spots and mild winds. When exposed to the direct sun, the heat index may augment by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'felt air temperature' or 'real feel', joins air temperature with relative humidity to produce a temperature perception for humans. One's perception of weather can be shaped by other factors, involving metabolic differences, pregnancy, and physical exertion. It is essential to be conscious of the fact that direct sunlight can intensify the felt heat, leading to an elevation in the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are highly critical for babies and toddlers. Children often overlook the necessity for resting and fluid replenishment. Thirst is a late sign of dehydration - thus, it is critical to stay hydrated, especially during extended periods of physical activities.

Humidity

The average relative humidity in September is 58%.

Rainfall

In Fullerton, during September, the rain falls for 3.5 days and regularly aggregates up to 0.2" (5mm) of precipitation. Throughout the year, in Fullerton, there are 52.5 rainfall days, and 7.09" (180mm) of precipitation is accumulated.

Daylight

In Fullerton, the average length of the day in September is 12h and 22min.
On the first day of the month, sunrise is at 6:26 am and sunset at 7:16 pm. On the last day of September, in Fullerton, California, sunrise is at 6:45 am and sunset at 6:36 pm PDT.

Sunshine

In Fullerton, the average sunshine in September is 10.6h.

UV index

June through September, with an average maximum UV index of 6, are months with the highest UV index. A UV Index estimate of 6 to 7 represents a high threat to health from unsafe exposure to UV radiation for ordinary individuals.
Note: The daily high UV index of 6 during September translates into the following recommendations:
Steer clear of overexposure. Fair-skinned individuals can be scorched in less than 20 minutes. Avoid direct Sun exposure from 10 a.m. to 4 p.m., a period when UV radiation is most intense, and remember that not all shade structures provide full protection. Sunglasses providing both UVA and UVB protection are non-negotiable on sunlit days.