when is flu season

Flu season in the Northern Hemisphere, including the United States, typically runs from October through April or May. It usually peaks during the colder months, with the highest flu activity most often occurring between December and February. Flu viruses spread more rapidly when temperatures are low and the air is dry. In the Southern Hemisphere, flu season generally occurs during their colder months, roughly from April through October or November. Overall, flu viruses can be present year-round, but the seasonal spikes correspond to the colder months of each hemisphere's winter.