Today's barometric pressure in San Francisco, a 48-hour pressure chart, and a risk score for weather-triggered migraine and headache, based on pressure drops, humidity, and temperature changes.
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San Francisco's famous fog is driven by pressure differentials between the cool ocean and warm interior valleys. These daily pressure shifts, combined with the city's microclimates, create a subtly challenging environment for migraine sufferers.
Worst season for migraines: February. Winter Pacific storms bring the most significant pressure drops to the Bay Area. The city's famous fog is itself driven by pressure differentials between the cool ocean and warm Central Valley, creating daily pressure oscillations even in calm weather.
Common triggers in San Francisco: Pacific storm fronts, fog-driven daily pressure oscillations, microclimate temperature differentials across the city. San Francisco's famous microclimates mean pressure and temperature can vary significantly within a few miles. The fog that rolls through the Golden Gate represents a measurable pressure event each time, and residents in different neighborhoods may experience different trigger levels on any given day.
Typical pressure: San Francisco averages 1016 hPa at rest, measured at the city's own elevation rather than corrected to sea level, and storm systems can push readings down to 1001 hPa. Swings of 4-8 hPa over 24 hours are common during active weather and fall within the range most associated with pressure-triggered migraines.
2026 index: San Francisco ranks #93 of 100 in our 2026 U.S. Migraine Risk Index, where #1 is the most challenging city for weather-driven migraine.
Can San Francisco weather trigger migraines?
Yes. San Francisco experiences 4-8 hPa barometric pressure swings, and research shows pressure drops are one of the most common migraine triggers. The city's specific patterns include Pacific storm fronts, fog-driven daily pressure oscillations, microclimate temperature differentials across the city.
What time of year are migraines worst in San Francisco?
In San Francisco the most barometrically volatile stretch of the year falls in February. That is when weather is most likely to play a part, if weather is a trigger for you at all. See when migraine weather season starts across the U.S.
Is there a barometric pressure headache forecast for San Francisco?
This page works as one. Many people call a headache that arrives with a weather change a barometric pressure headache, and this forecast tracks the pressure drops, humidity and temperature swings behind that idea. The score covers the next 24 hours in San Francisco and the chart shows the next 48. It is built on migraine research, so treat it as a rough guide for other headaches. A sudden, severe headache needs urgent medical care, whatever the weather.
Your own forecast
This page shows the weather risk for everyone in San Francisco. The MigrAid app learns yours. It saves the barometric pressure, humidity and temperature with every migraine you log, shows whether San Francisco's swings really line up with your attacks, and alerts you when conditions match your own trigger history.