Yes, it is still flu season. In the United States, flu season runs through the fall and winter, with activity peaking between December and February most years. As of early January 2026, flu activity is not only ongoing but increasing, with nearly 1 in 4 influenza tests coming back positive and almost 40,000 people admitted to hospitals with the flu in a single week.
Where Flu Activity Stands Right Now
The CDC’s most recent surveillance data paints a clear picture: flu is surging. The national influenza positivity rate hit 24.7% for the week ending January 3, 2026, and the trend is climbing. Hospital admissions for influenza rose to 11.8 per 100,000 people that same week, up from the prior week. Across the country, nearly 40,000 patients were admitted to hospitals with the flu in that seven-day window alone.
Long-term care facilities are seeing even steeper numbers, with hospitalization rates of 54.1 per 100,000 residents and rising. These figures suggest the 2025-2026 season is still intensifying rather than winding down.
When Flu Season Typically Peaks and Fades
Flu activity in the U.S. usually picks up in October or November, peaks somewhere between December and February, and tapers off by late March or April. That said, the exact timing shifts from year to year. Some seasons peak as early as December, others not until March. Influenza viruses actually circulate year-round at low levels, but the overwhelming majority of cases cluster in that winter window.
If you’re reading this in January or February, you’re likely right in the thick of peak season. By March and April, activity generally declines, though it doesn’t vanish overnight. Late-season flu cases are common well into spring.
Why Cold Weather Fuels the Flu
Flu isn’t just a winter illness by coincidence. The virus itself survives and spreads more effectively in cold, dry air. Research published in PLOS Pathogens found that influenza transmission was most efficient at low relative humidity (20% to 35%) and was completely blocked at 80% humidity. Temperature matters too: transmission occurred far more readily at 5°C (41°F) than at 20°C (68°F), and stopped entirely at 30°C (86°F).
Cold temperatures also extend the period during which an infected person sheds the virus at peak levels, by roughly 40 hours compared to warmer conditions. So in winter, people are not only more infectious for longer but the virus particles themselves are more stable in the air. Combine that with more time spent indoors in close quarters and you get the conditions for rapid spread.
Flu Season in the Southern Hemisphere
If you’re traveling internationally, keep in mind that flu season flips with the hemispheres. In countries like Australia, Argentina, and South Africa, flu activity typically runs from April through September, sometimes stretching into October or November. That means if you’re heading south of the equator during a Northern Hemisphere summer, you could walk straight into their flu season.
Flu vs. Allergies: Telling Them Apart
As flu season overlaps with early spring allergy season, it’s worth knowing which one you’re dealing with. The differences are fairly reliable.
- Fever: The flu commonly causes a high fever (100 to 102°F or higher) lasting 3 to 4 days. Allergies never cause fever.
- Body aches and exhaustion: Severe aches, fatigue, and a feeling of being wiped out at the start of the illness are hallmarks of the flu. Allergies don’t produce these symptoms.
- Itchy, watery eyes: This points strongly toward allergies. It’s rare with the flu.
- Duration: Flu rarely lasts beyond 2 weeks, though fatigue can linger for up to 3 weeks. Allergy symptoms persist as long as you’re exposed to the trigger, often 6 weeks or more during pollen season.
- Sneezing and runny nose: Both can cause these, but they’re more consistent with allergies. With the flu, a stuffy nose is only an occasional symptom.
The simplest rule of thumb: if you have a fever and body aches that came on suddenly, it’s far more likely to be the flu. If your eyes itch and your symptoms have dragged on for weeks without a fever, allergies are the more probable explanation.
What This Means for You
With flu activity still rising as of early January 2026, getting vaccinated remains worthwhile if you haven’t already. It takes about two weeks for the vaccine to build full protection, so even a mid-season shot can cover you through the remaining weeks of peak activity and beyond. The flu vaccine is updated each year to match circulating strains, so last year’s shot won’t help.
Basic precautions still make a measurable difference during active flu season. Washing your hands frequently, staying home when you’re sick, and avoiding close contact with people who have symptoms all reduce your risk. If you do get sick and develop a high fever, severe body aches, or difficulty breathing, those are signs you’re dealing with something more serious than a cold.