April Weather in Fullerton, United States

Last updated: June 24, 2025

In April, the average temperature in Fullerton, United States hovers around 9°C (49°F), with minimums dipping as low as -13°C (10°F) and maximums reaching a balmy 31°C (88°F). Be prepared for some moisture, as precipitation amounts to 57 mm (2.2 in) over 9 days, accompanied by an average humidity of 71%.

April Temperature in Fullerton

In April, Fullerton experiences an average temperature of 9°C (49°F), with maximums reaching up to 31°C (88°F) and minimums dropping to as low as -13°C (10°F). This temperature variability makes it essential for travelers to pack both warm and cool clothing options for their adventure.

April Weather in Fullerton: Daily Temperature Highs, Lows, and Averages

The chart illustrates April temperature patterns in Fullerton, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Fullerton, April typically has an average temperature of 9°C (49°F), with highs reaching up to 31°C (88°F) and lows dropping to around -13°C (10°F).

Data source: Temperature data for Fullerton generated using information from the Copernicus Climate Change Service.

April Precipitation in Fullerton

In Fullerton in April, the total precipitation amount is 57 mm (2.2 in) over the course of 9 days.

April Precipitation Trends in Fullerton

The chart displays monthly precipitation patterns in Fullerton, with values for each month alongside April’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how April’s conditions compare to those of other months. In Fullerton, April typically receives around 57 mm (2.2 inches) of precipitation spread over approximately 9 days.

Data source: Precipitation data for April generated using information from the Copernicus Climate Change Service.

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

April Humidity in Fullerton

In Fullerton in April, humidity is 71%. With an average temperature of 9°C (49°F), this humidity feels like a damp chill that seeps into your bones, making it essential to dress warmly and plan for cozy indoor activities while exploring the area.

April Average Humidity in Fullerton

This chart illustrates the average monthly humidity levels in Fullerton, with April’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In April, average humidity in Fullerton is approximately 71%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for April generated using information from the Copernicus Climate Change Service.

April UV Index in Fullerton

In Fullerton in April, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Fullerton.

Maximum UV Index Levels in Fullerton for April

The chart shows the monthly maximum UV Index (UVI) for Fullerton in April, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In April, the maximum UV index in Fullerton typically reaches 9, which falls under the very high exposure category.

Data source: Fullerton April UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

Extreme (11+): Avoid the sun, stay in shade.
Very High (8-10): Limit sun exposure.
High (6-7): Use SPF 30+ and protective clothing.
Moderate (3-5): Midday shade recommended.
Low (0-2): No protection needed.

How April Weather in Fullerton Compares to Other Months

Weather in Fullerton varies notably across the year, with each month offering distinct climate conditions. This page compares April’s weather to other months in Fullerton, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in Fullerton, showing how April’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-4°C (26°F)	28 mm (1.1 inches)	73%	moderate
February Weather	-4°C (25°F)	20 mm (0.8 inches)	81%	moderate
March Weather	4°C (40°F)	89 mm (3.5 inches)	69%	high
April Weather	9°C (49°F)	57 mm (2.2 inches)	71%	very high
May Weather	16°C (61°F)	142 mm (5.6 inches)	80%	very high
June Weather	24°C (75°F)	97 mm (3.8 inches)	83%	extreme
July Weather	25°C (78°F)	65 mm (2.5 inches)	84%	very high
August Weather	23°C (74°F)	84 mm (3.3 inches)	84%	very high
September Weather	20°C (69°F)	57 mm (2.2 inches)	77%	very high
October Weather	11°C (52°F)	83 mm (3.3 inches)	72%	high
November Weather	4°C (40°F)	22 mm (0.9 inches)	80%	moderate
December Weather	-1°C (31°F)	42 mm (1.6 inches)	79%	moderate