Does influenza peak in winter just because it’s colder?

Winter seasons often coincide with respiratory virus seasons in general—not just influenza, but other respiratory viruses like rhinovirus, adenovirus, and respiratory syncytial virus. It’s likely that these viruses are more common in winter for several different reasons, including (but not limited to) temperature, humidity, and human behaviour (spending more time indoors and with larger groups of people around the winter holidays). It’s important to note, though, that influenza epidemics in particular are incredibly difficult to predict—a lot of these factors are constantly changing, and so is the virus itself!