Why does low atmospheric pressure make you feel sleepy and drained?

Many people notice the same thing when the weather turns grey and a storm is on the way: eyelids feel heavy, thoughts slow down, and even a normal day feels like wading through treacle. This is one of the most common experiences that weather‑sensitive people describe — a wave of drowsiness and low energy when atmospheric pressure falls. It is real, it is widely reported, and there are several plausible reasons for it. But the honest picture is more nuanced than the popular one‑line explanation, so let's walk through it calmly and clearly.

First, what "low pressure" actually means

Atmospheric pressure is simply the weight of the air above you pressing down. It is measured in hectopascals (hPa) or millibars (mb) — the two are identical — and also in millimetres of mercury (mmHg). At sea level the long‑term average is about 1013 hPa (760 mmHg). Day‑to‑day it drifts up and down, roughly between 990 and 1030 hPa in most places.

"Low pressure" usually means a value below about 1009 hPa, and — this is the key part — low pressure almost always arrives together with a whole package of other weather: thick cloud, rain, higher humidity, wind, and a dimmer, greyer sky. That bundling matters a lot, because when your body feels sluggish on a low‑pressure day, the pressure number itself may be only one of several things acting on you at once. Untangling them is exactly what makes this topic interesting.

The popular explanation: "less oxygen in the air"

The explanation you will hear most often is that low pressure means less oxygen, so your brain gets less oxygen and you feel sleepy. There is a grain of truth here, but it is worth being precise, because the effect at sea level is much smaller than most people assume.

When air pressure drops, the air does become slightly less dense, so each breath contains marginally fewer oxygen molecules. However, the size of the everyday pressure swings we experience at ground level is small compared with what it takes to move your blood oxygen. A large population study in Norway — the Tromsø study, which measured blood oxygen saturation in more than seven thousand people — found that it took a pressure change of roughly 167 hPa to shift blood oxygen saturation by just 1 percent. Everyday weather rarely moves pressure by more than 20–40 hPa. In other words, the drop in available oxygen from a passing low‑pressure system is, for a healthy person at sea level, tiny — far too small on its own to explain a heavy wave of drowsiness.

This is different from mountains or aircraft. At high altitude the pressure is genuinely and persistently much lower, oxygen really does fall meaningfully, and fatigue from thinner air is well documented. But a rainy day in a lowland city is not remotely the same thing. So while "less oxygen" is not entirely wrong, it is almost certainly not the main reason most people feel tired when a low rolls in. That frees us to look at the more likely explanations.

The stronger explanation: light, or the lack of it

Here is where the "package deal" of low‑pressure weather really matters. Low pressure brings cloud and rain, and cloud dramatically cuts the amount of light reaching your eyes. A bright sunny day outdoors can deliver tens of thousands of units of light (lux); a heavily overcast day can be ten to a hundred times dimmer, and indoor lighting dimmer still.

Light is the single most powerful signal your body uses to keep its internal 24‑hour clock — the circadian rhythm — running on time. Bright morning and daytime light tells the brain, in effect, "it is day, be alert." One of the ways it does this is by suppressing melatonin, the hormone that makes you feel sleepy. Melatonin normally rises in the evening to usher in sleep and stays low during the day. Research shows that when daytime light is weak, melatonin is not suppressed as firmly, and studies confirm that melatonin present during the day increases subjective sleepiness. Melatonin is also made from serotonin, a chemical involved in mood and alertness, so dim days nudge this whole light‑sensitive system in the direction of feeling drowsy and flat.

So a large part of that "low‑pressure sleepiness" may in fact be low‑light sleepiness. The barometer is falling, yes, but the sky is also grey, and your circadian system is reading the gloom as a signal to wind down. For many people this is probably the biggest single contributor.

The autonomic nervous system and the inner ear

A newer and genuinely fascinating line of research looks at how the body might directly sense pressure changes. Scientists studying weather sensitivity have found that the inner ear — the same organ that handles balance — appears to act as a barometric pressure sensor. In laboratory studies, lowering the surrounding pressure activated balance‑related nerve cells, and in weather‑sensitive people, falling pressure was linked to shifts in the autonomic nervous system, the automatic control system that runs heart rate, blood pressure, digestion and arousal without your conscious input.

The autonomic system has two broad modes: a "get‑going" sympathetic side and a "rest‑and‑settle" parasympathetic side. Research suggests that pressure changes can tip the balance between them. When that balance shifts, some people feel it as fatigue, foggy‑headedness, dizziness or a drained, heavy sensation. This mechanism is still being actively studied and is not fully settled — much of the strongest evidence so far comes from animal experiments — but it offers a credible route by which the falling barometer, rather than just the accompanying gloom, could genuinely register in the body.

Blood pressure may play a part

Your own blood pressure is not fixed; it responds to many things, including the weather. Several studies of people with high blood pressure have found an inverse relationship between atmospheric pressure and blood pressure in certain seasons — that is, when the air pressure outside falls, blood pressure in some people tends to dip too (temperature and other factors also matter and can pull the opposite way, so this is a tendency, not a rule).

A modest dip in blood pressure can leave a person feeling tired, slow, lightheaded or short on energy, because for a short while slightly less blood is being pushed to the brain and muscles. People who naturally run on the lower side of normal blood pressure often say they feel this most. This is one more plausible thread in why grey, low‑pressure days can feel so heavy — though, as with everything here, it varies enormously from person to person.

Sleep quality the night before

Low‑pressure weather does not only affect how you feel during the day; it can also affect the night before. Warmer, more humid, stuffier air — which often accompanies low pressure — tends to make sleep lighter and more broken, and changing pressure is a commonly reported disturber of sleep. If your night's rest was shallower than usual, you will naturally start the next day with less in the tank. So part of the daytime tiredness people blame on the barometer may actually be an ordinary sleep‑debt effect wearing a weather costume.

The simplest explanation of all: behaviour

It is easy to overlook the most human factor. When the sky is dark, cold and wet, people move less. They skip the walk, stay indoors, curl up, drink another coffee, and generally shift into a lower gear. Less movement, less daylight exposure and a cosier, dimmer environment all naturally invite drowsiness. None of this requires any exotic physiology — it is simply how a grey day changes what we do, and behaviour has a powerful effect on alertness. Recognising this is oddly reassuring, because it is the part most within our own influence.

Why some people feel it and others don't

Perhaps the most important thing to understand is that responses to weather vary hugely between individuals. Some people sail through a plunging barometer without noticing a thing; others feel wiped out. This "weather sensitivity" is influenced by age, overall health, sleep habits, existing conditions such as migraine, and probably a genuine difference in how strongly each person's nervous system reacts to environmental change. If you are someone who reliably feels drained when a low arrives, that experience is valid — you are not imagining it — even though the exact mix of causes may differ from your neighbour's.

It is also worth keeping a sense of proportion. For the great majority of people, low‑pressure tiredness is an uncomfortable, passing nuisance that lifts when the weather clears, not a sign of anything dangerous. Noticing the pattern — and planning gentler, lighter days around it — is usually the most useful response.

What the science does and doesn't say

To be honest about the state of the evidence:

• It is well established that dim light and disrupted circadian signalling increase daytime sleepiness, and low‑pressure weather reliably brings dim light. This is probably the strongest explanation.
• It is fairly well supported that pressure changes can shift the autonomic nervous system and blood pressure in sensitive individuals, which can translate into tiredness — though the size of the effect differs from person to person.
• It is largely a myth that everyday sea‑level pressure drops starve your brain of oxygen; the measured oxygen change is far too small.
• The inner‑ear pressure‑sensing mechanism is a promising, active area of research but is not yet fully confirmed in humans.

In short: yes, feeling sleepy and low on energy when the pressure falls is a real and common experience, but it is usually a combination of dim light, altered nervous‑system and blood‑pressure responses, poorer sleep and quieter behaviour — not simply "not enough oxygen."

A gentle, non‑medical note

Occasional tiredness that tracks the weather and lifts when conditions improve is a familiar part of life for many weather‑sensitive people. If, however, fatigue is persistent, severe, or clearly out of step with the weather, or comes with other symptoms that worry you, that is a conversation worth having with a qualified health professional — the weather is only ever one of many things that can affect how you feel. This article explains known mechanisms and patterns; it is not a diagnosis or a treatment plan.

One of the most useful things you can do is simply to notice your own pattern. Tracking how you feel alongside the day's pressure and sky over a few weeks — the kind of record MeteoStorms is designed to make easy — can show you whether your energy really does dip on low‑pressure days, by how much, and how quickly it recovers. That personal picture is far more informative than any single rule of thumb.

Sources

• Smith, D. et al. The effect of atmospheric pressure on oxygen saturation and dyspnea: the Tromsø study. International Journal of Biometeorology / PubMed, 2020. https://pubmed.ncbi.nlm.nih.gov/32125519/
• Sato, G. et al. Lowering barometric pressure induces neuronal activation in the superior vestibular nucleus in mice. PLOS One, 2019. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0211297
• The inner ear is a barometric pressure sensor — change in barometric pressure induces vestibular ganglion cell activation in mice. Scientific Reports (Nature), 2025. https://www.nature.com/articles/s41598-025-28093-4
• Cipolla‑Neto, J. & Amaral, F. The Role of Melatonin in the Circadian Rhythm Sleep‑Wake Cycle. Psychiatric Times / peer‑reviewed literature on melatonin and light. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6767594/
• A Meteorological Paradox: Low Atmospheric Pressure‑Associated Decrease in Blood Pressure… Atmosphere (MDPI), 2022. https://www.mdpi.com/2073-4433/13/2/235
• Evaluation of the impact of atmospheric pressure in different seasons on blood pressure in patients with arterial hypertension. PubMed, 2016. https://pubmed.ncbi.nlm.nih.gov/27518887/
• NOAA Space Weather Prediction Center (space‑weather and geomagnetic data context). https://www.swpc.noaa.gov/