For an adult bearded dragon, aim for a basking surface in the high 90s to low 100s °F, measured with an infrared temp gun. The cool-end air should fall within the Merck Veterinary Manual’s preferred range of 25–32°C (77–90°F). Keep humidity low: Merck lists 20–30% relative humidity, and many hobbyist care sheets allow a little more. Turn all lights and heat off at night, and add dark heat only when the enclosure drops well below the daytime range.

Those figures look like they disagree with each other, and that confuses many keepers. This guide covers what most care sheets skip. The published numbers measure different things, so the guide sorts them out first. Then it gives you a measure → diagnose → fix workflow for when your thermometer readings don’t match any of them.

Why the published numbers disagree

Care sheets and veterinary references measure in different places. Merck’s 77–90°F is an air temperature range, the “preferred optimal temperature zone” a dragon moves around in. The 95–110°F figure repeated across hobbyist care sheets is a surface temperature, the top of the basking rock directly under the lamp. A rock in sunlight is hotter than the air around it, and in an enclosure the same thing happens under a basking bulb. Both numbers can be right in the same enclosure.

Merck also gives a basking zone about 5°C above the top of the range, and a night temperature about 5°C below the bottom of it. Converted, that puts basking air at roughly 99°F just above the platform and night air at roughly 68°F. Cool-side figures vary across sources mostly because people measure them at different heights and distances from the lamp.

Number-reconciliation table

Figure you’ll see quoted	Where it comes from	What it actually measures	Where to put the probe	Use it as
77–90°F (25–32°C)	Merck Veterinary Manual	Air temperature across the usable gradient	Digital probe at dragon height: one near the warm end (not under the lamp), one at the cool end	Your air targets. Warm-end air near the top of this range, cool-end air near the bottom.
Basking about 5°C above that range (~99°F)	Merck	Air just above the basking platform	Probe a few inches above the platform, out of the dragon’s reach	A check that the hot zone is really hot, not just one hot spot on the rock
95–110°F basking	Common hobbyist care-sheet figure	Surface of the basking rock or platform	Infrared temp gun pointed at the exact spot where the dragon’s back sits	Your surface target. Juveniles are usually kept toward the hotter end, adults toward the lower end.
Night about 5°C below the range (~68°F)	Merck	Night air	Cool-end probe, read before you go to bed and again in the morning	Your night floor. Add heat only if the enclosure drops clearly below it.
20–30% RH	Merck	Relative humidity of the enclosure air	Hygrometer mounted centrally on the back wall, away from the water dish and the corners	Your baseline. Slightly higher readings are common in hobbyist setups and aren’t a crisis on their own.

In short: use a temp gun for the basking surface, digital probes for the air, and the right target for each one.

What temperature should a bearded dragon’s basking spot be, and is that the surface or the air temperature?

Both, measured separately. The care-sheet range of 95–110°F is a surface temperature. Read it with an infrared thermometer pointed straight at the platform. The air a few inches above the platform should sit around Merck’s basking figure, roughly 99°F. If the surface reads hot but the air above it is barely warm, the bulb is making a small hot patch, not a basking zone. The dragon can cook its belly without warming its body. A wider flood bulb or a broader, flatter platform usually fixes this.

Hatchlings and juveniles are normally kept nearer the top of the surface range and adults nearer the bottom. Let behavior guide the final setting. A dragon that basks, warms up and moves off on its own is using the gradient correctly.

Does a bearded dragon need heat at night, and how cold is too cold?

Usually not. Bearded dragons are semi-arid Australian lizards, and their native habitat cools off at night. The NSW Department of Education’s inland bearded dragon guide describes setting up the enclosure around a day-heat gradient, not round-the-clock warmth. Turn the basking lamp and UVB off at night.

Add heat only when the enclosure falls clearly below Merck’s night figure of about 68°F. That often happens in a cold basement, a drafty room or a winter house with the thermostat turned down. Use a heat source that gives no light, such as a ceramic heat emitter (CHE) or a deep heat projector, on its own thermostat. Don’t use red or blue “night bulbs.” They still give off light the dragon can see, and they break up its day-night cycle.

What humidity should a bearded dragon tank be, and why does it go up at night?

Keep it low. Merck lists 20–30% RH, and many hobbyist care sheets accept somewhat higher. Most homes stay in a workable range without any help. Don’t mist routinely.

The night rise usually happens because the temperature dropped, not because moisture was added. Relative humidity is a percentage of how much water the air could hold. Cooler air holds less, so the same amount of water vapor reads as a higher percentage once the lamp goes off. Before you remove the water dish, check whether the night temperature fell too far. Fixing that, or improving ventilation, often brings humidity back down on its own.

Merck also notes that humidity needs rise during shedding (ecdysis). A small rise while your dragon sheds is expected, not an emergency.

How do I lower humidity in a glass bearded dragon tank?

Work through these in order:

Check the hygrometer’s position. A sensor in a corner, near the substrate or over the water dish reads high. Mount it centrally on the back wall at dragon height.
Improve ventilation. A glass tank with a mostly solid lid traps moisture. A screen top or added vents is the main fix.
Move the water dish to the cool end and use a smaller one. Water evaporates much faster under the basking lamp.
Change the substrate if you use something that holds moisture, such as damp soil mixes or coconut fiber kept wet. Tile, paper or a dry, loose substrate holds far less.
Correct the night temperature if the spike only happens after lights-out (see above).
Stop misting unless a vet has told you to for a specific reason.

How do I know if my bearded dragon is too hot, and how do I cool the tank?

Sitting with the mouth open (gaping) while basking is normal thermoregulation, so it isn’t a warning sign by itself. Signs of overheating include:

Panting or gaping that continues after the dragon has left the basking spot
Staggering or uncoordinated movement
Refusing food along with avoiding the warm end entirely
Pressing against the coolest glass or hiding at the cool end all day

To cool the tank:

Raise the lamp or the fixture.
Use a lower-wattage bulb.
Use a dimming thermostat to bring the output down.
Lower the basking platform away from the bulb.

If the cool end won’t drop, the enclosure is usually too small for the lamp, or the room itself is too hot. A sunny window can heat a glass tank far past any lamp. If you see the movement or breathing signs above, take the dragon off heat to a cool, shaded part of the enclosure and call an exotic vet.

The measure → diagnose → fix workflow

Step 1: Measure the right things

You need:

An infrared temp gun for the basking surface.
At least two digital probe thermometers, one at the warm end and one at the cool end, at dragon height. A single thermometer can’t show you a gradient.
A digital hygrometer, mounted centrally on the back wall.

Take readings once the lamps have been on long enough to warm up, then again after lights-out. Write them down. Patterns over several days are more useful than any single reading.

Step 2: Diagnose with the symptom → cause → fix matrix

Symptom	Most likely cause	Fix
Basking surface below your target	Bulb wattage too low, lamp mounted too high, or platform too far from the bulb	Raise the platform, use a stronger flood bulb, or raise the dimmer setting. Re-measure after it warms up.
Basking surface hot, but air above it barely warm	Narrow spot bulb making a small hot patch	Switch to a wider flood bulb, or use a larger, flatter platform
Basking surface above your target	Platform too close or bulb too strong	Lower the platform or reduce the dimmer setting. Never run a basking bulb without a thermostat.
Cool end won’t fall into Merck’s range	Enclosure too small for the lamp, a solid lid trapping heat, or a hot room	Use a lower-wattage bulb, add ventilation, move the tank away from windows and heat vents, or upgrade the enclosure
Warm end air too low even though the basking surface is correct	Cold room pulling heat out of the enclosure	Insulate the back and sides, or add a second basking bulb on the same thermostat
RH jumps above daytime levels after lights-out	Temperature drop, not added moisture	Check the night temperature first. If it falls below the night floor, add a lightless heat source on a thermostat. Then re-check RH.
RH high during the day too	Poor ventilation, water dish under the lamp, or damp substrate	Improve ventilation, move the dish to the cool end, and switch substrate
RH rises while the dragon is shedding	Expected higher humidity need during ecdysis (Merck)	Leave it, unless sheds start getting stuck repeatedly
Dragon avoids the basking spot	Too hot, or the surface heats unevenly	Measure the surface with the temp gun. Lower the output and watch behavior over several days.

Step 3: Fix one thing at a time

Change one variable and re-measure after the enclosure settles, then change the next. If you swap the bulb, move the platform and change the lid all at once, you won’t know which change fixed the problem or created a new one.

Worked example: a dragon whose readings match nothing

Setup: An adult dragon in a 4 × 2 × 2 ft glass-front enclosure with a mostly glass lid. The house is around 70°F by day and drops to the low 60s at night in winter.

Readings:

Basking surface (temp gun): 88°F
Air above the platform: 84°F
Cool-end air: 80°F
Cool-end air at night: 62°F
Hygrometer: 35% by day, 58% at night

Diagnosis, one line at a time:

Basking surface 88°F. This is below the care-sheet surface range, and the air above the platform is well short of Merck’s basking figure of about 99°F. The bulb isn’t strong enough at that distance.
Cool end 80°F. This is within Merck’s 77–90°F air range, so it needs no change.
Night 62°F. This is about 6°F below Merck’s night figure of roughly 68°F. The dragon needs a little dark heat.
Night humidity 58%. This is almost certainly caused by the temperature drop. Suppose the air holds the same amount of moisture and is warmed from 62°F to 68°F. Basic vapor-pressure physics says relative humidity would fall to about 47%, with no change to the water dish.
Day humidity 35%. This is slightly above Merck’s figure and within what many keepers run. Leave it alone for now.

Fixes, in order:

Raise the basking platform closer to the bulb, or move up to a stronger flood bulb on a dimming thermostat. Re-measure until the surface and the air above it both reach target.
Add a ceramic heat emitter on a separate thermostat, set to the night floor. It should only switch on when the room gets cold.
Check the hygrometer the next night. If humidity is still high at a correct temperature, replace part of the glass lid with screen.

Here, the obvious fix (removing the water dish to cut humidity) would have treated the wrong problem.

Equipment: what the setup actually needs

Job	Equipment	Notes
Daytime basking heat	Halogen or incandescent flood bulb, or a mercury vapor bulb	Bearded dragons bask under light and heat together, as they would under the sun. A CHE gives no light and isn’t a basking source.
Controlling basking heat	Dimming thermostat with its probe at the basking zone	Secure the probe where the dragon can’t move it. On/off thermostats make halogen bulbs flicker.
UVB	A desert-strength linear T5 tube spanning much of the enclosure, inside the enclosure or over thin mesh	Replace it on the manufacturer’s schedule, because UVB output fades before the visible light does
Night heat (only if needed)	CHE or deep heat projector on its own thermostat	Lightless, so it doesn’t disturb sleep
Measurement	Temp gun, two or more digital probes, hygrometer	Glass stick-on thermometers can’t read surface temperature and often read inaccurately

UVB is as important as heat. Bearded dragons are sun-basking lizards. In the UV-Tool study by Baines et al., they’re grouped with the species that need fairly strong UVB exposure close to their basking spot. Without enough UVB, dragons can’t use dietary calcium properly. Lamp placement and distance matter as much as the bulb itself. See Bearded Dragon Lighting Requirements: UVB and Heat Explained for the full lighting setup.

Common mistakes

When to see an exotic vet

Book an appointment with an exotic or reptile vet if you see:

Open-mouth breathing at rest away from the basking spot, wheezing, or mucus or bubbles at the nostrils or mouth
Lethargy together with refusing food, especially when your temperatures measure correctly
Stuck sheds that keep happening, particularly around the toes and tail tip
Trembling, swollen limbs, a soft or misshapen jaw, or difficulty walking
Any signs of overheating (panting away from the heat, staggering) that don’t settle once the dragon is in a cooler area

Not every general-practice vet treats reptiles. When you call, ask: “Do you have a vet who sees reptiles?” For a vet-school reference to compare your setup against before the appointment, see the Royal Veterinary College’s bearded dragon care sheet.

The short version

Measurement	Tool	Target
Basking surface	Temp gun	High 90s to low 100s °F for adults. Hotter for juveniles.
Air above basking platform	Digital probe	About 99°F (Merck’s basking figure)
Warm-end air	Digital probe	Toward the top of 77–90°F
Cool-end air	Digital probe	Toward the bottom of 77–90°F
Night air	Digital probe	No lower than about 68°F. Add dark heat only below that.
Humidity	Hygrometer, mounted centrally	Low: Merck lists 20–30%, and a little higher is common

If your readings don’t match, decide whether the problem is surface temperature, air temperature, night temperature or humidity. Then fix one variable at a time and measure again.