How we calculate it
For each place we take the hourly forecast for the next 24 hours and compare it with the day before. Every factor scores from 0 to 1 and is multiplied by its weight. The weights reflect how strong the evidence is.
- 40%Pressure drop within 24 hoursCounts from a 3 hPa drop and is full at 10 hPa. Attacks became more frequent after drops of more than 5 hPa a day (Kimoto 2011; review by Farah 2025).
- 25%Temperature swing within 24 hoursCounts from 3 °C and is full at 10 °C, both warming and cooling. Temperature was the strongest weather factor in a 2025 meta-analysis (OR 1.15).
- 15%Fast pressure changeThe largest change within 3 hours, from 2.5 to 5 hPa. Below that are normal daily pressure tides, especially in the tropics.
- 10%Low pressureFull between 1003 and 1008 hPa, slightly below the standard 1013 hPa, where a study from Japan saw the most attacks (Kimoto 2011). Based on a single study, so it carries a smaller weight.
- 10%Strong windCounts from 25 km/h and is full at 45 km/h. In Calgary, attacks were more likely on chinook days with wind above 38 km/h (Cooke 2000).
Index from 30: elevated. From 55: high. Alerts go out from the level you choose.
How to read the index
The index describes the weather in your area for the next 24 hours. Humidity is not included: a 2025 meta-analysis found no significant link. Weather sensitivity is individual, so compare the index with your own attacks and report them here. We refine the model with every MigraineWatch report.
Sources
- Kimoto K, Aiba S, Takashima R, et al. Influence of barometric pressure in patients with migraine headache. Intern Med. 2011;50(18):1923-1928.
- Farah A, Adam Y, Ahmed O, et al. Impact of barometric pressure changes on the severity, frequency, and duration of migraine attacks: a systematic review of the literature. Cureus. 2025;17(11):e96821.
- Li S, Liu Q, Ma M, Fang J, He L. Association between weather conditions and migraine: a systematic review and meta-analysis. J Neurol. 2025;272:346.
- Mukamal KJ, Wellenius GA, Suh HH, Mittleman MA. Weather and air pollution as triggers of severe headaches. Neurology. 2009;72(10):922-927.
- Yang AC, Fuh JL, Huang NE, et al. Patients with migraine are right about their perception of temperature as a trigger: time series analysis of headache diary data. J Headache Pain. 2015;16:49.
- Cooke LJ, Rose MS, Becker WJ. Chinook winds and migraine headache. Neurology. 2000;54(2):302-307.
- Hoffmann J, Lo H, Neeb L, Martus P, Reuter U. Weather sensitivity in migraineurs. J Neurol. 2011;258(4):596-602.
Experimental feature, not medical advice. Weather is one of several migraine triggers. If your headaches change, become more frequent or severe, see a doctor.