Flu Season Timeline

When flu season starts, peaks, and ends by US region — plus the best time to get vaccinated and high-risk population guidance

The flu season timeline shows when influenza activity typically begins, peaks, and ends by US region. Flu timing varies each year — check CDC FluView for current season activity at your location.

US Flu Season by Region

Peak activity Moderate activity Baseline/low

Vaccination Timeline

Sep–Oct
Ideal window — Get vaccinated now; protection develops in ~2 weeks, in time for peak season.
Nov–Dec
Still effective — Good protection, especially if flu season starts late in your region.
Jan–Feb
Late but worthwhile — Season typically continues through March/April; vaccination still provides benefit.

How to Use the Flu Season Timeline

The flu season timeline shows typical activity patterns. Actual onset and peak vary by year, influenced by which influenza strains are circulating, population immunity levels, and chance. The CDC FluView dashboard (cdc.gov/flu/weekly) provides current season data updated weekly.

High-Risk Groups

Adults 65+, children under 5 (especially under 2), pregnant women, and those with chronic conditions (asthma, diabetes, heart disease, obesity, immunosuppression) are at highest risk for flu complications. These groups should prioritize early vaccination and prompt antiviral treatment (oseltamivir/Tamiflu) within 48 hours of symptom onset.

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FAQ

Is this flu season timeline free?

Yes, completely free with no signup. Find flu season timing for your US region instantly.

When does flu season typically start?

In the US, flu season typically begins in October, peaks between December and February, and ends by April. The exact timing varies each year. Southern states tend to see earlier flu activity; Northern states often peak later. The CDC tracks flu activity weekly at cdc.gov/flu.

When is the best time to get a flu shot?

September through October is ideal — early enough to be protected before flu season peaks, but not so early that immunity wanes before late-season flu. If you missed the window, get vaccinated anyway; even a January flu shot provides protection. Annual vaccination is recommended because flu viruses change each year.

How long does the flu last?

Uncomplicated influenza typically lasts 5-7 days for most healthy adults, though fatigue and cough can persist for 1-2 weeks. High-risk individuals (older adults, young children, immunocompromised, pregnant women) are more likely to develop complications requiring medical care.

What is the difference between flu and COVID-19?

Flu and COVID-19 share many symptoms (fever, cough, fatigue, body aches). COVID-19 more commonly causes loss of smell/taste and has a longer incubation period. Testing is the only reliable way to distinguish them. Both can cause severe illness; vaccination is available for both.