Fullerton's winters are mild, with temperatures rarely dipping below 2°C or rising above 30°C in January and December. Spring brings a gradual warming trend, with April and May averaging around 17°C, but March remains relatively cool. Summer is warm, with June to August temperatures often reaching highs of 37°C, while September cools slightly before October's temperatures dip back down. Autumn is mild, with November and December temperatures returning to the cooler range seen in winter.