The aura is the blood pulling back.

Migraine moves the blood, not just the nerves.

The aura is a wave of blood flow. The shimmer or the blind spot that can precede the pain is not only a nerve event. A wave of intense firing and then silence, cortical spreading depression, sweeps across the surface of the brain at about three to four millimetres a minute, and a wave of lower blood flow travels with it. The first blood-flow recordings of attacks caught it: flow rose briefly, then fell into a spreading oligemia that crept forward across the back of the brain, ignoring the borders of the big arteries.¹ Modern fMRI has since clocked that same slow march across the human visual cortex,² and perfusion scans during an aura measure the dip directly, a 16 to 53 percent fall in local flow with no sign of a true stroke.³ The aura you see is, underneath, the blood drawing back.

A single attack clears, but over the years migraine leaves a faint mark, and it shows up in the vessels. In a population brain-scan study, people with migraine, especially those with aura, carried more silent infarcts in the back of the brain, and women with migraine more deep white-matter spots, than people without it.⁴ Pooled across studies, migraine with aura roughly doubles the long-run risk of an ischemic stroke, while migraine without aura barely moves it.⁵ The risk to any one person stays small, but it is real, and it is why a headache belongs on a site about blood flow.

Even on a clear day a migraine brain holds its flow a little less steadily. Between attacks, people with aura show impaired cerebral autoregulation, the reflex that keeps flow constant when pressure shifts,⁶ and migraine carries a measurable dip in the autonomic control of the circulation.⁷ That is the bridge to the weather below: a system with less margin to steady itself takes an outside knock, like a falling barometer, harder than one with room to spare.

What a falling barometer does.

A falling barometer is the single strongest weather predictor of a migraine attack, found in the largest objective headache study to date.

If a turning sky reliably brings on your head pain, you are not imagining it, and you are not alone. Weather is one of the most commonly reported migraine triggers, named by roughly half of migraine patients, and the link holds up when the studies are pooled: across 31 studies, weather change as a reported trigger carried a risk difference near 0.47, with lower air pressure independently tied to attacks.⁸

The largest objective test agrees with what people describe. In a smartphone study of 336,951 logged headache events, a falling barometer, and in particular a pressure drop in the roughly six hours before onset, was the single strongest weather predictor of an attack.⁹ That is why the pain often arrives before the front fully does.

And it does not take a storm. Independent diary studies place the trigger at small drops of about 5 to 10 hPa below normal, ordinary passing weather rather than altitude or a real low-pressure system.¹⁰¹¹ A sensitive person notices fronts that most people sleep through, which is exactly the experience that tends to get dismissed.

What weather changes is the wiring, and it is not an oxygen problem. A falling barometer does not meaningfully lower the oxygen reaching your brain. The air is still 21 percent oxygen, and weather shifts pressure only slightly; one large population study found it would take an enormous drop, far beyond any weather, to shave even one percent off blood-oxygen.¹² What changes is the signal.

The sensor is in the inner ear. In animals a small pressure drop activates it, lights up a specific brainstem relay, the superior vestibular nucleus, and runs on through the autonomic and trigeminal pathways that generate migraine; removing the inner ear abolishes the effect.¹³¹⁴ That chain is mapped step by step in rodents. In people we see the matching pattern and the matching biology, but the connecting wires are inferred, so in us this stands as a strong mechanism rather than a proven cause.¹⁵

This is where it ties into the rest of this site: barometric headache runs on the same autonomic and vascular controls as the rest of it. Migraine travels closely with POTS and dysautonomia, so the shared-wiring idea is grounded in real comorbidity.¹⁶ And the populations this page is about do have measurably poorer control of their brain blood flow: reduced cerebral blood-flow velocity on standing turns up in about 92 percent of long-COVID and 88 percent of ME/CFS patients.¹⁷ A system with less margin to hold its flow and autonomic tone steady plausibly absorbs an outside knock worse, so a passing front may land harder. Whether these groups are actually more weather-sensitive than everyone else has not been tested head to head, so the page treats it as a reasonable expectation and no further.

Be calibrated about the size of it. The average effect is real but small: the pooled pressure association is modest, weather accounts for roughly 20 percent of attacks, and the signal is for how often attacks come, with no consistent effect on how bad or how long they are.¹⁸¹⁵

A vivid personal pattern and a faint group signal are both true at once. More people feel weather-sensitive than diary studies can confirm as individuals, and the belief itself does not predict who actually tracks the weather,¹⁵ yet within the genuinely sensitive subgroup the effect can be large, and the pull is not limited to migraine: in a citizen-science study of chronic pain, low-pressure, humid, windy days raised the odds of a painful day by a small but real margin.¹⁹ So your barometer story can be entirely real even though it would barely register in an average.

What to actually do on a bad-weather day: cool down, take salt and fluids if your blood pressure and kidneys allow, and wear waist-high compression. Those do more than watching the barometer ever will, because for the standing symptoms the bigger weather culprit is heat, not pressure: warming the body opens the skin's vessels and pulls blood from the head, dropping brain perfusion sharply.²⁰ You cannot change the sky, so spend your effort there. And if you treat migraine, a falling-pressure forecast is most useful as a cue to take your acute medication early, at the first sign, which is when it works best.

Migraine, on its own terms.

The aura is itself a blood-flow event and the long-run vascular risk is real but small; the headache mechanism is well mapped. Here is the full verdict and evidence.

Migraine travels with the standing illnesses. If yours comes with dizziness or fog on standing, see standing intolerance. Headache that started after a head injury usually takes a migraine form, see concussion and TBI. It also tracks the hormonal cycle, so the menopause transition matters, and what helps has the practical steps.