When Is Flu Season? 7 Questions and Answers About Peak Flu Months

Medically Reviewed By Avi Varma, MD, MPH, AAHIVS, FAAFP
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Flu season generally begins in October and ends in May in the United States. Peak months for flu activity are December through February, but you can take steps to lower your risk of flu, including getting a flu shot. Throughout the year, researchers monitor flu trends around the world to make predictions about the upcoming flu season in the U.S. This information also helps determine which flu strains will make up each year’s vaccine.

This article will discuss when flu season is, its peak months, and how experts monitor flu activity. It will also explain how you can protect yourself and your family during flu season, including when to get a flu shot.

1. When is flu season?

Sleepy child in bed possibly sick with flu
Eloisa Ramos/Stocksy United

Flu season typically starts in October in the United States, according to the Centers for Disease Control and Prevention (CDC).

Flu infection rates in the U.S. increase beginning in October and tend to peak from December to February. However, it is possible to get the flu during any time of year.

Flu season in the U.S. usually ends by May, according to the CDC. A 2022 research article notes that the 2021-2022 season extended into June. However, it adds that this was an unusual flu season.

2. What are the peak flu season months?

February and December are the two peak months for flu season in the U.S. This is based on a CDC analysis of nearly 40 years of data.

Peak flu months in the U.S.

Following is a rank of peak months for flu. It is based on the number of years each month had the highest flu activity.

  1. February
  2. December
  3. January
  4. March
  5. November
  6. October
  7. April

Peak flu activity may vary depending on the state where you live. Check information from your local health department about flu case rates and severity in your area.

3. How do experts predict and monitor flu season?

In addition to monitoring flu activity, health experts also use flu forecasting to predict trends for the upcoming flu season.

In 2013, the CDC began collaborating with a variety of external research teams to build predictive models for upcoming flu seasons. Through this project, the CDC designated two National Centers of Excellence for Influenza Forecasting. One is at Carnegie Mellon University and the other at the University of Massachusetts Amherst.

Using data from past flu seasons, flu forecasters can generate predictions about the upcoming season, including:

  • the strains of virus
  • the geographical areas most at risk
  • the timing of flu activity peaks

This information can help guide flu vaccine composition and distribution, among other public health responses.

Southern hemisphere flu season

Flu forecasters in the northern hemisphere also evaluate each year’s preceding flu season in the southern hemisphere, which runs from June to September.

In a 2022 letter to The Lancet, researchers note that the 2022 flu season in Australia started earlier than in past years. It also had record high rates of flu.

Experts warn this could indicate a similarly severe 2022-2023 flu season in the U.S. and elsewhere in the northern hemisphere.

Seasonal flu vaccine development

Infectious disease scientists also study the pattern of flu strains around the world. This helps them make predictions about which strains are likely to be most dominant in the upcoming U.S. flu season.

Each year, groups including the Food and Drug Administration (FDA) and the National Institute of Allergy and Infectious Diseases (NIAID) work to identify three or four likely dominant flu strains. This process occurs months prior to flu season. It allows time for the design and production of vaccine doses to fight those specific strains.

Learn more about the effectiveness of seasonal flu vaccines.

4. What are ways to prevent seasonal flu?

If you are eligible, getting a flu vaccine every year is the most effective way you can prevent seasonal flu, according to the CDC.

The National Institute on Aging (NIA) also provides recommendations to prevent seasonal flu and limit its spread to others.

Flu prevention tips

In addition to receiving an annual flu vaccine if you are able, you can help prevent flu with the following steps:

  • Wash your hands often, particularly after touching high-traffic surfaces such as door knobs or phones.
  • Avoid touching your face, especially your nose, eyes, and mouth.
  • Keep surfaces in your home clean with soap and disinfectants.
  • Cover your mouth and nose when you sneeze or cough to prevent the spread of droplets.
  • Try to avoid close contact with anyone who you know has the flu.
  • If you have flu symptoms, stay home from work or school, if possible.

If you get the flu, the CDC recommends staying home when possible. Remain at home until you have not had a fever for at least 24 hours and your fever goes away on its own, without medication. This can help prevent the spread of the flu virus to others.

Contact your doctor for guidance about your symptoms and when you can return to normal activities.

Learn 11 high-risk groups for flu.

5. When is the best time to get the flu vaccine?

The NIA recommends getting a flu vaccine by the end of October.

If flu activity has increased earlier in your area, your doctor may recommend getting a flu shot sooner, such as in September.

However, a 2019 study of flu seasons from 2010–2017 found that the effectiveness of the flu vaccine can decrease over time. According to researchers, the likelihood of a person testing positive for flu increased by 16% every 28 days from the time of vaccination.

Each flu season is unique, and different seasonal strains or activity patterns may change vaccine recommendations. Talk with your doctor or healthcare professional about flu shot timing that is right for you.

Can you get the flu vaccine and COVID-19 vaccine at the same time?

It is safe to get your flu vaccine and any COVID-19 vaccine at the same time, according to the CDC. This includes initial and follow-up doses.

6. How can parents protect children against seasonal flu?

Any child 6 months and older who is eligible should receive a yearly flu shot. This is according to recommendations from the American Academy of Pediatrics.

The CDC notes that children ages 5 and younger are at higher risk for complications from flu. Children under the age of 2 are at especially high risk.

Parents and caregivers should also get an annual flu shot to help prevent the spread of flu among household members. Additionally, doctors recommend that anyone who is pregnant receive a flu vaccine.

If your child has flu symptoms, keep them home from school until they have not had a fever for at least 24 hours.

Caring for young children when you have the flu

If you are sick with the flu and care for children under the age of 5, the following are steps you can take to prevent its spread:

  • Try to limit direct physical contact with your child except when necessary.
  • Wash your hands before and after picking up, feeding, changing, or comforting your child.
  • Cover your mouth when you cough or sneeze, particularly when around young children.
  • Keep frequently touched surfaces such as counters or keyboards clean and disinfected.
  • Take any prescribed antiviral medications as directed to help treat your flu as soon as possible.

It is important to watch your child for any signs of flu. Contact your pediatrician right away if your child develops flu-like symptoms.

Learn 5 myths about the flu.

7. What other respiratory viruses circulate during flu season?

The months of flu season also have increased activity of other respiratory viruses.

A 2022 study looked at rates of viral infections over five flu seasons from 2016–2021. It found that other non-influenza respiratory viruses were prevalent during these seasons, including:

  • Adenovirus: This is a common virus that causes cold- and flu-like symptoms.
  • Seasonal coronavirus: Coronaviruses are a group of viruses that can cause respiratory illness. SARS-CoV-2 is a new, or novel, type of coronavirus that causes COVID-19.
  • Human metapneumovirus (hMPV): This is a common virus that causes an upper respiratory infection.
  • Respiratory syncytial virus (RSV): This virus causes an infection of the lungs and airways. It is very common among children.

Learn more about RSV symptoms, transmission, and treatments.

Preventive measures for these respiratory viruses are similar to those for the flu. Talk with your doctor or pediatrician about the most effectives ways to protect yourself and your family.


Flu season in the United States typically begins around October and ends in May. However, each flu season can vary, and some may be longer or shorter.

Infectious disease scientists monitor trends and develop flu forecasts. This helps guide the development of the vaccine for each flu season. The flu vaccine contains the three or four strains experts think will be most dominant that year.

Getting a flu shot for yourself and your children is the most effective way to prevent flu. Healthy habits can help reduce transmission of the flu virus. These include washing hands often, keeping surfaces clean, and covering your nose and mouth when you sneeze.

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Medical Reviewer: Avi Varma, MD, MPH, AAHIVS, FAAFP
Last Review Date: 2022 Oct 10
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