How I picked these: how they work, specs and buyer reviews. I haven't owned every one of them.
What to expect
- A barometer gives hints, not a forecast. It tells you what the air pressure is doing where you are. That says a lot about the next 12 to 24 hours, but nothing like a Met Office forecast built from satellites and computer models.
- The trend matters more than the number. Whether the needle is rising or falling, and how fast, tells you more than where it points. The words on the dial ("Rain", "Change", "Fair") are a rough guide only.
- It must be set for your height. Pressure drops as you go up, by about 1 hPa for every 8 metres. Unset, a barometer on a hill will read "Rain" for ever.
- A storm glass doesn't forecast. It's pretty, but tests show its crystals mostly follow temperature, not the weather to come. I'd buy one as an ornament, not an instrument.
Why these
An aneroid barometer uses a sealed metal capsule instead of a column of mercury. It's small, safe, works at any angle on a wall and needs no liquid. Old mercury barometers are lovely but hold a toxic metal.
Barometer, thermometer and hygrometer in one frame. Temperature and humidity help make sense of the pressure, and one hole in the wall is better than three.
Good barometers have a second, movable pointer on the glass. You park it on today's reading, so tomorrow you can see at a glance which way the needle has gone.
It shows the temperature using nothing but floating glass. It's not precise, but it's a working physics lesson on a shelf.
Humidity matters indoors: too high and you get condensation and mould. A small dial hygrometer can live in the room that worries you.
Listed here because people ask. It's a curiosity. Buy it if you like the look, and don't plan a walk on it.
How they work
The aneroid barometer
The heart of it is a flat, round metal capsule with ridged sides, sealed with most of the air taken out. A spring stops it collapsing. When air pressure rises, it squeezes the capsule a tiny amount. When pressure falls, the capsule springs back out.
The movement is far too small to see, so a lever multiplies it. The lever pulls a fine chain wrapped around a spindle, and the spindle turns the pointer. A hairspring keeps the chain tight. That's why a tap on the glass sometimes makes the needle jump: the linkage has a little friction in it.
The Galileo thermometer
A sealed glass tube of clear liquid with glass bulbs floating in it. Each bulb is weighted to a slightly different density and carries a tag with a temperature. As the room warms, the liquid expands and gets less dense, so bulbs sink one by one. The temperature is shown by the lowest bulb that's still floating; the real figure sits between that and the highest sunk bulb.
Hygrometers and storm glasses
A dial hygrometer measures humidity with something that changes length when damp. Old ones used a human hair, which stretches slightly in moist air. Most cheap dial ones now use a coiled strip that winds and unwinds with humidity and turns the needle directly.
A storm glass is a sealed tube of camphor and other chemicals dissolved in alcohol and water. Crystals grow and dissolve inside it, and folklore says their shapes predict the weather. When people have tested this, the crystals mostly track temperature, and they don't give a reliable forecast.
What to buy
These are on Amazon UK, checked 7 November 2026. Listings change, so check each one before you order.
These are affiliate links. If you buy through them I make a small commission, at no extra cost to you. It helps cover the cost of running this site. This is a hobby, not a shop.
Barometers
Weather glasses
Not on Amazon
Set it up
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Pick the spot
An inside wall, at eye level, away from radiators, fires, direct sun and outside doors.
Why: the barometer itself copes with indoor temperature, but sun and heat make the thermometer and hygrometer read wrong and can stress the movement. Eye level means you'll actually look at it.
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Let it settle for a day
Hang it and leave it 24 hours before setting.
Why: it has been in a cold van and a warm house. The metal needs time to settle at room temperature.
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Find today's sea-level pressure
Look up the current pressure at your nearest weather station on the Met Office website. That figure is already corrected to sea level. Pick a calm day, when pressure isn't changing fast.
Why: every barometer dial is marked for sea level. Setting it to the sea-level figure takes your height out of the reading, so "Fair" and "Rain" mean what they should.
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Tap, then adjust the screw
Tap the glass gently with a fingertip. Then turn the small adjusting screw on the back with a screwdriver until the needle points to the Met Office figure. Turn it slowly; a small turn moves the needle a long way.
Why: the tap frees any friction in the linkage so you're setting the true position, not a stuck one.
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Check it a week later
Compare it with the Met Office figure again on another calm day. If it's out by more than a hPa or two, adjust again.
Why: a new movement can creep a little at first. One check after a week usually sorts it.
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Test the hygrometer with salt
Put a spoonful of table salt in a bottle cap, add a few drops of water to make a damp paste (not a puddle). Seal it in a food bag with the hygrometer for 8 to 12 hours at steady room temperature. It should read about 75%. Note how far off it is, or adjust it if there's a screw on the back.
Why: air sealed over damp salt settles at about 75% humidity, a fixed point of physics. Dial hygrometers often drift, so this gives you a known reference for free.
Reading it
Keep a 9am log
Every morning at the same time: tap the glass, read the needle, note it in a notebook with what the sky is doing. Then move the set hand onto the needle. Tomorrow, the gap between the two tells you the change since today.
The same time each day matters because pressure has a small natural rise and fall through the day. A fixed time cancels that out.
What the trend means
The Met Office uses these words for how fast pressure is changing in its shipping forecasts. They're a good scale to think in:
| Change in 3 hours | Called | Rough meaning |
|---|---|---|
| under 0.1 hPa | Steady | More of the same. |
| 0.1–1.5 hPa | Rising / falling slowly | A slow change on the way, often over a day or more. |
| 1.6–3.5 hPa | Rising / falling | Falling: cloud, wind and rain becoming more likely. Rising: clearing, often breezy and showery at first. |
| 3.6–6.0 hPa | Rising / falling quickly | Falling quickly: a low is coming, expect wind and rain. |
| over 6.0 hPa | Very rapidly | Strong winds and possibly gales likely soon. |
These are rules of thumb, not promises. High and steady pressure usually means settled weather: dry, and in winter often cold, foggy or frosty. Low and still falling is the classic sign of a depression coming in from the Atlantic.
Normal UK pressure sits roughly between 980 and 1040 hPa, around an average of about 1013. Some dials are marked in inches of mercury; 1013 hPa is about 29.92 inches. hPa and millibars are the same thing.
Looking after them
- Don't knock it hard. A gentle tap is fine. A hard knock can bend the chain or damage the capsule.
- Re-check the setting once a year against the Met Office figure.
- Hair hygrometers like a bit of moisture. If an old hair type sticks, wrapping it in a damp cloth for an hour often frees it. Then redo the salt test.
- Galileo thermometer: keep it upright and out of direct sun. Moving it about too much can knock the tags.
Common problems
| What you see | Likely cause | Fix |
|---|---|---|
| Always reads "Rain" or "Stormy" | Not set for your height | Set it to the Met Office sea-level figure. |
| Needle jumps when tapped | Normal friction in the linkage | Tap before every reading. A jump of a hPa or so is fine. |
| Needle never moves at all | Linkage stuck, or capsule damaged | Watch it over a stormy week. If it still doesn't move, it needs a repairer. |
| Drifts away from the Met Office figure | New movement settling, or a tired old capsule | Reset it after a week. If it keeps drifting, follow the changes, not the number. |
| Hygrometer stuck on one value | Dried-out hair or a sticking coil | Damp-cloth trick for hair types, then the salt test. Cheap coil types may just need replacing. |
| All Galileo bulbs at the top or bottom | Room colder or warmer than its range | Normal. It reads only within the range of its tags. |
| Storm glass looks the same for weeks | Steady room temperature | Expected. It responds mostly to temperature. |
Safety
- Galileo thermometers and storm glasses are glass full of liquid that isn't safe to drink, and a storm glass contains alcohol. Keep them out of reach of children and pets, and don't try to open them.
- If one breaks, ventilate the room, wear gloves to pick up the glass and wipe up the liquid. Check the maker's leaflet for what's inside.
- Mercury barometers: if you inherit or buy an old one, don't tip it or take it apart. Mercury vapour is toxic. Leave moving and repair to a specialist restorer.
Notes
The aneroid barometer was invented by Lucien Vidi in the 1840s, which is why the capsule is sometimes called a Vidi capsule. Admiral Robert FitzRoy, who founded what became the Met Office, pushed for barometers in fishing ports in the 1850s and 60s and wrote simple rules for reading them. The pressure tendency words above are the ones used in the shipping forecast. The 75% salt figure is the standard humidity reference for saturated table salt at room temperature.
The Galileo thermometer is named after Galileo because it works on principles he studied. The design itself came later, from scientists in Florence.
Related guides: needle meters, compasses and sundials, mechanical watches, Stirling engines.