Foster City's climate is mild and temperate, with temperatures gradually warming up as the year progresses. In winter, temperatures range from freezing to moderate, averaging around 10°C in January and 11°C in February. As spring arrives, temperatures rise steadily, reaching averages of 14°C in April and 17°C in May. Summer months bring warm temperatures, with July and August averaging 22°C, while autumn sees a slight cooling trend, returning to average highs of around 16°C by October. Winters are generally cool, with December temperatures averaging just 8°C.