Can a migraine weather forecast app actually predict your next attack?

Short answer: a migraine weather forecast app can be predictive for pressure-sensitive sufferers — but only after you’ve logged enough attacks to know your threshold and your lead time. The population averages from the literature (a 6–10 hPa drop has been associated with attacks in small clinical cohorts, per Kimoto et al., 2011, n=28) are a starting point, not a forecast. A real personal forecast needs 30+ logged attacks overlaid against historical pressure data. Without that, even the best weather app is just guessing at a stranger.

Here’s how forecasting actually works, where it goes wrong, and how to build a forecast that’s calibrated to you.

How migraine forecasting actually works

The core idea is mechanical, not magic. Atmospheric pressure drops in advance of storm fronts — usually 12–48 hours before precipitation hits. If pressure is one of your migraine triggers, the drop itself (not the storm) is the signal.

A useful forecast does three things:

1. Reads a pressure curve — current pressure plus the next 24–72 hours of forecast pressure.
2. Detects a drop that exceeds a threshold (yours, ideally; the population average if not).
3. Alerts you with enough lead time to actually do something useful — 6–24 hours is the sweet spot.

The math is simple. The hard part is the inputs. Forecast pressure data isn’t always accurate beyond 48 hours, and ambient pressure varies by altitude — a 1010 hPa reading at sea level isn’t the same body experience as 1010 hPa adjusted from 2000m elevation.

Where the data comes from

If you’re an iOS user, there are two pressure sources worth knowing:

• The iPhone’s built-in altimeter (CMAltimeter API). Every iPhone since the 6 has a barometric sensor. It reports real-time station pressure — the actual air pressure your body is in right now. Surprisingly accurate, surprisingly underused.
• Apple WeatherKit. Pulls from a blend of sources including NOAA, government meteorological agencies, and proprietary models. Provides hourly forecast pressure, humidity, temperature for up to 10 days.

For everyone else, NOAA’s public APIs and OpenWeatherMap offer similar forecast data. The quality is comparable for the first 24–48 hours.

Crucially: a forecast is only useful if you can log against it. A pressure number with no attack history attached is wallpaper.

The false-positive problem

Here’s where most migraine weather apps fail.

Not every pressure drop triggers an attack. In a typical temperate climate, you’ll see 8–15 pressure drops per month that exceed the 6 hPa threshold. If you got a migraine every time, you’d be disabled. Most pressure-sensitive sufferers actually attack on only a fraction of qualifying drops — in my own ~400-attack log it’s closer to 1 in 3 — with the rest depending on co-factors like sleep deficit, dehydration, hormone phase, or stress load (see the top 30 migraine triggers ranked by real-world frequency).

So a naive forecaster sends you 10 alerts a month, you get 3 migraines, and you stop trusting the app. The alerts become noise.

The fix is two-layered:

1. Personal threshold. Your number is almost certainly not the population average. Some people react to 4 hPa, others to 12.
2. Co-trigger context. A pressure drop on a night of poor sleep is meaningfully different from one after a good week. The best forecasters weight pressure alerts against your recent sleep, hydration, and cycle data.

You won’t get to a useful signal-to-noise ratio in the first month. Anyone promising 90% prediction accuracy out of the box is selling you a horoscope.

How to find your personal threshold

You can do this manually if you don’t mind a spreadsheet. The recipe:

1. Log every attack with a timestamp for at least 8 weeks. Even Notes app entries work.
2. Pull historical hourly pressure for your location (NOAA’s archive is free).
3. For each attack, look at the 24 hours before it. Plot the pressure curve.
4. Calculate the average drop. That’s your threshold.
5. Then check the non-attack days. How many qualifying drops happened that didn’t trigger an attack? That’s your false-positive rate. Adjust your threshold upward until the false-positive rate is tolerable (mine sits around 30%).

This is tedious but it works. The first time you see your own attacks line up against the pressure curve, it’s hard to unsee. For a deeper dive on the underlying research and the barometric pressure threshold, see the long-form post. (For a written log without an app, the migraine diary template covers the minimum fields.)

How a migraine weather forecast app should work (Migra’s approach)

I built Migra in part because I got tired of doing the spreadsheet by hand. A few specifics on how it forecasts:

• Dual pressure source. Live readings come from the iPhone’s CMAltimeter (the same chip that powers floor counting in Apple Health). Forecast pressure comes from Apple WeatherKit. Live + forecast = a continuous curve from “right now” to ~72 hours ahead.
• Personal threshold detection. After ~30 logged attacks, on-device AI (Apple Foundation Models, iOS 26+) starts surfacing your specific drop threshold instead of the 6–10 hPa population average. Everything stays on your phone — no cloud, no scraped data.
• Alerts 6–24 hours ahead when the forecast curve crosses your threshold. Throttled to one alert per hour so a noisy night doesn’t wreck your sleep.
• False-positive feedback loop. When you mark an alert as a false alarm, the model learns. Threshold tightens. Alerts get rarer and more accurate.

Before 30 attacks, Migra uses population thresholds and is upfront about it: the forecast is generic. After 30, it’s yours.

What a forecast can’t do

A few honest limits worth saying out loud:

• It can’t predict non-weather-triggered migraines. If pressure isn’t one of your triggers (a meaningful minority per clinical surveys, e.g. Okuma 2015), this whole technology stack is useless to you. The best migraine tracker app comparison covers options if pressure isn’t your dominant trigger.
• It can’t beat forecast error. If the meteorological forecast is wrong by 4 hPa at 48 hours out, the migraine forecast inherits that error.
• It can’t replace abortive medication or trigger hygiene. The forecast buys you a head start. What you do with the head start is the actual treatment.

But the head start is real. The gap between “this happens to me randomly” and “I have 12 hours of warning” is the entire reason I keep working on this thing.