When Is Flu Season?

First, know that flu season dates vary from year to year, but here's you can expect.

woman wrapping a blanket around herself in bed
Photo: Yelizaveta Tomashevska/Getty Images

When you're trying to squeeze every last beach hang, outdoor workout, and frozen drink that you can out of your summer, the last thing you want to think about is the flu. But flu season can be just as seemingly premature as the arrival of pumpkin spice-everything in August. If you're not already mentally preparing yourself right about now, you might want to start. (

Most years, flu season lasts from late fall through early spring, but it can be longer or shorter. "The exact timing and length of flu season varies from year to year, but most of the time flu activity begins to increase in October and peaks between December and February," says Norman Moore, Ph.D., director of infectious diseases scientific affairs for Abbott. "However, flu viruses can continue to circulate as late as May." Talk about an awful spring fling. (

One of the main factors that affects the length of a given flu season is the timing of that year's predominant strain or strains of the influenza virus. "The duration of the flu season can be affected by factors such as circulation of different strains of the virus at different times, which happened in the 2018-2019 season," explains Moore. As a reminder, last year the strain H1N1 dominated from October through mid-February and H3N2 peaked from February through May, resulting in the longest flu season on record of the last 10 years.

And as far as the best time to get the flu shot or the flu vaccine nasal spray? There's no time like the present. Experts recommend getting vaccinated before the season even starts. "The best time to get vaccinated is late September," Darria Long Gillespie, M.D., an ER doctor and author of Mom Hacks, previously told us. If you want to get ahead of the game, the 2019-2020 flu vaccine is already available. It might feel early to take that step, but one flu-related death has already been reported in California.

So, while you can rely on September or October as the best time to get vaccinated, the beginning, end, and peaks of a given flu season are less predictable. Here's to hoping this year's flu season is shorter than the last.

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