"There is no link for you"

That's the answer no forecasting service can ever give you. And for many people, it's the most valuable one.

0.59. That's how well one of the newer headache-attack prediction models could tell a day with an attack apart from a day without, when it was tested on new patients in an eight-week prospective study at two American university hospitals. A model guessing completely at random would score 0.5. The model scored 0.59 — and was also poorly calibrated: it rated the risk higher than it actually was.

That's not an argument that the field is poorly researched. It's an argument that predicting an individual attack, even with the best tools available, still stands on weak ground. A service that promises to tell you when you'll feel bad promises more than the numbers behind it can support.

An app that only speaks when it thinks there's something

That's the very construction of a forecasting service: it says something when it believes the risk is high, and says nothing the rest of the time. That silence looks like an answer, but it isn't one. It never tells you "I've looked, and there's nothing" — because it only ever looks for the one outcome it's built to warn about.

A review of the literature on weather and migraine concludes, after weighing findings with and without a connection against each other, that no causal link between weather and migraine patterns has been demonstrated. Weather appears as a contributing factor among many, not as a main cause. That's not the same as saying weather is irrelevant for everyone. It's a reminder that an average across a whole population can't tell any one person what applies to them specifically.

The answer that never becomes a notification

There's an answer no forecasting service can give you by its very nature: that there's nothing to warn about. Not because nobody looked, but because someone looked, and there was no connection to find in you specifically. That answer requires someone to actually ask the question on the days when nothing in particular happens — not only on the days when something might.

The value of that answer isn't small. It means you can stop checking the forecast every morning to guess whether the day will be good or bad. You can set that worry down, not because anyone has promised that weather is innocent in general, but because your own data, over time, showed no pattern in you.

The reverse holds too. If you do find a connection, it isn't a promise about what happens tomorrow either — just better background to carry with you than a feeling is.