Short answer: most people with migraine get warning signs in the 2 to 48 hours before head pain begins. The most common are unusual fatigue, repeated yawning, mood changes, food cravings, neck stiffness, and frequent urination. The collection of these symptoms is called the prodrome, and recognising your own pattern is one of the most useful things you can do for your migraine care.

This page lays out the typical warning signs, the timing window to watch, and how Hermly’s risk forecast complements your subjective experience.

The most common warning signs, ranked

In population studies of self-reported migraine prodromes, the following symptoms come up most often, in roughly this order of frequency:

1. Unusual fatigue or tiredness

Not the normal end-of-day tiredness — a heavier, flatter feeling that’s out of proportion to what you’ve done. Often described as “I just feel off” or “I have no energy”. Reported by 60–70% of people who notice prodromes.

2. Repeated yawning

Specifically, frequent yawning that isn’t explained by sleep deprivation. The proposed mechanism involves hypothalamic dopamine release — yawning is part of a broader autonomic shift in the prodromal phase. Quirky but one of the better-validated signs.

3. Mood changes

Irritability is the most common, but anxiety, depression, or even a brief euphoria appear in different individuals. Often the person doesn’t notice the mood shift themselves — a partner or coworker spots it first.

4. Food cravings

Specifically for salt, chocolate, or specific carbohydrates. This is a major source of the “food triggers” misconception: the craving is driven by the prodrome, not the other way around. See our food trigger page for the direction-of-causation discussion.

5. Neck stiffness or soreness

Frequently mistaken for the cause of the migraine (“I slept wrong”) rather than recognised as an early symptom. If you find yourself rubbing your neck before an attack consistently, that’s the prodrome.

6. Frequent urination

Driven by hypothalamic changes affecting antidiuretic hormone release. Often combined with increased thirst.

7. Sensitivity to light or sound

A milder version of the photophobia / phonophobia that will become intense during the attack — already detectable hours before.

8. Difficulty concentrating or word-finding lapses

Subtle but consistent. People describe “brain fog” or “I can’t find the right word for something I’d normally know”.

The timing window

For most people, prodrome appears in the 12–24 hours before headache onset, but the full range is 2 to 48 hours. Two important patterns:

  • Within-person consistency. The window tends to be stable for the same individual. If your prodrome usually appears the evening before an attack, it will probably keep doing so.
  • Symptoms aren’t synchronised. Different prodromal symptoms often appear at different times — mood change might be 36 hours ahead, food cravings 12 hours ahead, the fatigue right before.

Tracking which symptoms appear when, across several attacks, will reveal your personal pattern faster than reading a generic list.

When you’ll see nothing

Roughly 30–40% of people with migraine don’t notice any prodrome. Reasons vary:

  • It may genuinely be absent — some attacks come on with no warning.
  • The signs may be too subtle to register without active tracking.
  • Some prodromal symptoms (mood shifts, fatigue) might be attributed to normal daily variation.

If you’re in this group, you may benefit more from Hermly’s forecast — because the model can detect physiological signals (HRV, sleep, pressure, cycle) that often shift during the prodromal window even when no subjective symptom is obvious.

How Hermly’s forecast relates to subjective warning signs

Hermly does not detect prodromal symptoms — there’s no sensor for “are you yawning more than usual?”. What Hermly does is forecast the next-24-hour risk based on physiology and environment.

The two signals — Hermly’s forecast and your subjective prodrome — are best read as independent inputs to the same question:

  • Both signals agree (forecast high + you feel prodromal): high confidence an attack is approaching. Plan accordingly.
  • Hermly high, you feel fine: the model sees physiological signals (sleep dropped, pressure falling) that haven’t reached your conscious awareness yet. Sometimes attacks follow; sometimes they don’t.
  • Hermly low, you feel prodromal: trust yourself. Your subjective experience is the ground truth for your attacks; the model is a supplementary read.
  • Both low: unlikely but not impossible — migraine has real randomness.

What to do with early warning signs

This is where Hermly stops giving advice. Acute migraine medications (triptans, gepants, ditans) can be more effective when taken during the prodromal phase or at first sign of attack. The PRODROME trial (2023) showed measurable benefit for at least one preventive medication taken during a recognised prodrome.

Whether and what to take is a conversation with your doctor — ideally one you have before the next attack, so you have a plan in place. Hermly will not prompt you to take medication, even on a 95% risk day.

What Hermly will do is mark the risk window clearly, give you the three factors that moved the prediction, and stay quiet so your decision is yours.