Costa Mesa's winters are mild, with temperatures ranging from around freezing to the mid-20s, averaging a relatively cool 14°C in January and December. Spring brings gradual warming, with April and May temperatures peaking in the mid-30s Celsius on average. Summers are warm to hot, with July and August often reaching highs of up to 35°C, while September's temperatures return to a more moderate range. Autumn is characterized by mild days and cooler nights, with October and November averaging around 18°C.