LOS ANGELES — Six years after the initial COVID-19 wave reshaped daily life, California health officials report that the virus is increasingly behaving like a summertime threat rather than a winter one. The pattern, already visible the past few years, became clearer in 2026 and has prompted public health leaders to adjust prevention priorities for the warmer months.
Summer surges outpacing winter
Data from federal and state sources show COVID activity rising across most of the country, and California is among the places seeing notable summer-level transmission. The U.S. Centers for Disease Control and Prevention currently estimates that COVID-19 is growing or likely growing in 43 states, with California listed among four states reporting moderate or high wastewater viral activity.
“Our summer peak was much higher in 2025 than it was in the winter,” Dr. Erica Pan, director of the California Department of Public Health, said at a recent briefing. “Summer is really the bigger peak. So if you do have patients or loved ones who have not gotten the ‘25-‘26 vaccines, it is still effective and highly recommended, given this surge we’re starting to see.”
That shift runs counter to the typical seasonal pattern for respiratory illnesses, which usually intensify in colder months when people spend more time indoors. COVID’s evolving seasonality now resembles an uncommon pattern among respiratory pathogens.
How the numbers compare
Emergency department visit data highlight the divergence between summer and winter activity. Nationally, COVID-related emergency visits topped out last summer at about 1.7% of all visits, while the winter peak reached around 1%. California’s summer peak in 2025 was higher still — roughly 2.1% — compared with a minimal winter peak near 0.2%.
| Jurisdiction | Summer peak (2025) | Winter peak |
|---|---|---|
| National | 1.7% | 1% |
| California | 2.1% | 0.2% |
State health officials say these trends warrant a recalibration of messaging and prevention efforts, including vaccination campaigns timed for when infection risk rises.
What officials are recommending
California’s top public health official has urged residents to consider vaccination if they or their loved ones have not yet received the 2025–2026 COVID vaccine. The department emphasizes that the shot remains an effective tool to reduce severe illness and hospitalizations.
- Get vaccinated if eligible, especially those who haven’t received the 2025–2026 formulation.
- Seek testing if symptomatic or after known exposure.
- Use appropriate precautions in high-risk settings, such as hospitals and long-term care facilities.
Public health authorities in California and elsewhere are also watching wastewater surveillance and clinic visit data to detect rising trends early and to guide localized responses.
Context and implications
The early pandemic years saw multiple waves in both summer and winter, with winter surges historically causing the most severe outcomes. In contrast, recent surveillance indicates the more pronounced peaks are now occurring during warmer months, a change that affects how health departments schedule outreach and where residents choose to take precautions.
For most people, COVID today remains less deadly than at the pandemic’s height, thanks in part to vaccines and prior infections that provide population-level immunity. Still, health officials stress that vulnerable groups — including older adults, people with weakened immune systems and those with chronic conditions — continue to face greater risks and should follow guidance on vaccination and other protective measures.
As California navigates these changing patterns, experts say continued monitoring and timely public messaging will be essential to limit severe outcomes and to keep hospitals from becoming strained during unexpected surges.
Reporting contributed by public health briefings and federal surveillance summaries.
