May Weather in Fullerton, United States

Last updated: June 24, 2025

In Fullerton, United States, the average temperature in May is a pleasant 18°C (64°F). Expect a range that can dip to a minimum of 11°C (52°F) and peaking at a warm 30°C (86°F). During this month, precipitation is recorded at 12 mm (0.5 in) over approximately 3 days, with an average humidity of 70%. Perfect weather for exploring!

May Temperature in Fullerton

In May in Fullerton, the average temperature is 18°C (64°F). The maximum can reach 30°C (86°F), while the minimum can drop to as low as 11°C (52°F). This pleasant weather makes it an ideal time for travelers to explore the sights and enjoy outdoor activities.

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

The chart illustrates May 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, May typically has an average temperature of 18°C (64°F), with highs reaching up to 30°C (86°F) and lows dropping to around 11°C (52°F).

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

May Precipitation in Fullerton

In Fullerton in May, the precipitation amount is 12 mm (0.5 in) during a span of 3 days.

May Precipitation Trends in Fullerton

The chart displays monthly precipitation patterns in Fullerton, with values for each month alongside May’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how May’s conditions compare to those of other months. In Fullerton, May typically receives around 12 mm (0.5 inches) of precipitation spread over approximately 3 days.

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

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

May Humidity in Fullerton

In Fullerton in May humidity is 70%. With an average temperature of 18°C (64°F), this humidity feels like a sticky embrace, making outdoor excursions a bit more cumbersome and requiring frequent breaks to stay refreshed and hydrated.

May Average Humidity in Fullerton

This chart illustrates the average monthly humidity levels in Fullerton, with May’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In May, average humidity in Fullerton is approximately 70%, offering insight into how humid the weather typically is during this month.

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

May UV Index in Fullerton

In Fullerton in May, 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 Fullerton.

Maximum UV Index Levels in Fullerton for May

The chart shows the monthly maximum UV Index (UVI) for Fullerton in May, 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 May, the maximum UV index in Fullerton typically reaches 10, which falls under the very high exposure category.

Data source: Fullerton May 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 May 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 May’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 May’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	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