How much does barometric pressure have to drop to trigger a migraine?

If you’re reading this, you’ve probably said some version of “I can feel a storm coming” — and your friends thought it was metaphor.

It’s not. Barometric pressure changes are one of the most-cited migraine triggers in clinical literature, second only to stress. The question that people actually want answered isn’t whether pressure causes migraines (~75% of sufferers report it does, per Okuma et al., 2015) — it’s how much of a drop it takes.

Here’s what the research suggests, what my own logged data confirms, and what to do about it.

The short answer

A drop of 6–10 hPa within 24 hours is the most-commonly-cited threshold for triggering an attack in pressure-sensitive sufferers. But individual variation is huge:

• Highly sensitive people react to drops of 3–5 hPa
• The “average” sensitive sufferer reacts at 6–10 hPa
• Less sensitive people may need a 15+ hPa drop

The rate of change matters more than the absolute pressure. A slow drop over 3 days is gentler than a 6 hPa drop over 6 hours, even if the totals match.

Where the research stands

The most-cited paper on this is Kimoto et al. (2011), a Japanese study that tracked 28 migraineurs against ambient pressure data over a year. They found a statistically significant correlation between pressure drops of 6–10 hPa in a 24-hour window and migraine attacks within the following 24–48 hours.

A 2015 follow-up by Okuma et al. surveyed 295 patients and found 75% reported weather as a trigger, with low atmospheric pressure being the single most-common subtype (44% of weather-triggered cases).

What the research does not yet tell us:

• Why some people are pressure-sensitive and others aren’t
• Whether sensitivity is genetic, hormonal, or both
• Whether intervention (preventive meds taken pre-emptively at the threshold) actually changes outcomes vs. taking them at first symptom

Your personal threshold is what matters

Population averages are useful for talking to your neurologist. They’re not what you should optimize for.

The real question: what’s your threshold? The answer is buried in the correlation between your pressure data and your attack data. Most people have never plotted this. If you have 50+ logged attacks with timestamps, you can find your number.

This is the entire reason Migra exists. The app pulls real-time pressure from the iPhone’s built-in altimeter (yes, the iPhone has one — it’s how the elevator-floor-counting feature works) and historical pressure from Apple WeatherKit. It overlays your attack timeline against the pressure curve. After ~30 attacks, the on-device AI starts flagging your specific drop threshold.

What to do tonight

If you suspect pressure is one of your triggers, here’s the cheap experiment:

1. Get a pressure source. Migra’s free tier shows real-time pressure on the dashboard — no signup, no email. Or use any weather app that displays atmospheric pressure (most don’t, by default; you have to enable it).
2. Log every attack with a timestamp. Even just notes app entries are fine.
3. After 8 weeks, look at the 24 hours before each attack. Was pressure dropping?
4. If yes, calculate the average drop. That’s your threshold.

Once you have a threshold, the leverage is huge. You go from “I get migraines randomly” to “I get migraines when pressure drops X hPa, and I can take my abortive medication 6 hours earlier than I usually would.”

That single change — earlier intervention — is what turns weather-triggered migraines from disabling to manageable.

Worth knowing

• Pressure changes during airline travel are dramatic (cabin pressure simulates ~2400m altitude = ~750 hPa). About 35% of pressure-sensitive migraineurs report attacks during or after flights.
• Storm systems and seasonal transitions are the heaviest pressure-change events. Spring and fall produce the most weather-triggered migraines in temperate climates.
• The combination of falling pressure + rising humidity is more potent than either alone.

The pressure isn’t going to stop dropping. But the gap between “this happens to me” and “I know when this happens to me” is the entire game.