Quick Answer
- Basking spot: about 95–100°F (35–38°C) on the basking surface.
- Warm daytime air: mid-80s to about 90°F (29–32°C).
- Cool side: about 75–80°F (24–27°C).
- Night: commonly 70–80°F (21–27°C); add a heat source that gives off no light if your room gets colder.
- Humidity: about 70 percent or higher, with many care sheets citing 70–90 percent.
Why Temperature and Humidity Matter
Iguanas are ectotherms. They cannot make their own body heat, so they move between warm and cool spots to control their temperature. Body temperature drives almost everything an iguana does: digestion, appetite, immune function, activity and even how well it sheds. A green iguana that stays too cool cannot digest its plant diet properly and becomes sluggish and prone to illness. One that cannot escape the heat can overheat quickly.
Humidity matters because green iguanas come from humid tropical forests. Dry air contributes to dehydration, stuck shed and, in some cases, respiratory problems. Getting both numbers right, and measuring them instead of guessing, is one of the most important parts of iguana care.
Published ranges differ a little between care sheets, so the figures below are the commonly recommended ranges for green iguanas, not exact targets. Watch your iguana's behavior too: an iguana that basks all day with its mouth open may be too hot, while one that rarely leaves the basking spot may be too cold.
The Ideal Iguana Temperature Gradient
A temperature gradient is a range of temperatures within one enclosure, hottest under the basking lamp and cooler further away. It lets the iguana warm up and cool down as it needs.
| Zone | Fahrenheit | Celsius | Where |
|---|---|---|---|
| Basking surface | 95–100°F | 35–38°C | Top shelf, directly under heat and UVB |
| Warm daytime air | 85–90°F | 29–32°C | Upper part of the enclosure |
| Cool zone | 75–80°F | 24–27°C | Lower part, away from the lamps |
| Night | 70–80°F | 21–27°C | Whole enclosure, lights off |
Some guides, including PetMD, give an overall range of about 80 to 100°F during the day. A few UK care guides aim for a basking air temperature as high as about 99–104°F (37–40°C) at the very top of a tall enclosure. The principle is the same: a hot spot the iguana can sit in, and plenty of space that is noticeably cooler.
The Basking Spot
The basking spot should be wide enough for the iguana's whole body. Several moderate heat lamps spread over a long shelf work better than one very hot bulb. Measure the surface temperature where the iguana actually lies, not the air near the bulb. See our iguana lighting guide for bulb choices and placement.
Nighttime Temperatures
A drop at night is natural and healthy, but an iguana should not get cold. Most care sheets recommend keeping nights around 70–80°F. If your home drops lower, add a heat source that produces no visible light, such as a ceramic heat emitter or a radiant heat panel on a thermostat. Turn off all lights so the iguana gets a proper dark period.
How to Heat an Iguana Enclosure
- Daytime basking heat: halogen flood or incandescent basking bulbs over the basking shelf, on a dimming thermostat.
- Night heat (if needed): ceramic heat emitters or radiant heat panels on a thermostat.
- Room heat: in large room-sized enclosures, a safely installed room heater may be needed to keep the whole space warm.
Always guard bulbs and emitters the iguana can reach, and avoid heat rocks and under-tank heat mats as the main heat source. Iguanas can be badly burned by hot surfaces because they may not move away quickly enough.
Iguana Humidity Requirements
Green iguanas generally do best at about 70 percent relative humidity or higher. Care sheets commonly cite 70–90 percent, and some aim around 80 percent. Humidity tends to drop in heated homes during winter and in enclosures with mesh walls or tops, so check it regularly.
| Humidity | What it means |
|---|---|
| Below about 60% | Too dry; watch for stuck shed and signs of dehydration |
| About 70–90% | The commonly recommended range for green iguanas |
| Constantly wet surfaces | Too damp; risk of mold, bacteria and skin problems |
The goal is humid air with good airflow, not a soggy enclosure. Standing water on surfaces and wet substrate that never dries out can cause skin infections and mold.
How to Raise Humidity
- Add a large water container. A big, shallow tub raises humidity and gives the iguana somewhere to soak. Placing it in a warmer area increases evaporation.
- Mist the enclosure. Hand misting or an automatic misting system adds moisture. Mist plants and surfaces, not directly into the iguana's face.
- Use a reptile fogger or a room humidifier. Clean them often, as standing water in these devices can grow bacteria.
- Reduce open mesh. Partly covering mesh sides or tops with solid panels holds moisture in. Never cover the area under the UVB lamp with glass or plastic.
- Add live or artificial plants. Foliage helps hold humidity and gives cover.
How to Lower Humidity
If the enclosure stays too wet, improve ventilation, reduce misting, move water containers to a cooler spot and replace any substrate that stays damp. Wipe away condensation and check corners for mold.
Tools to Measure and Control the Environment
| Tool | What it does |
|---|---|
| Digital thermometers with probes | Show air temperature in the warm and cool zones at the same time |
| Infrared temperature gun | Measures basking surface temperature exactly where the iguana lies |
| Digital hygrometer | Measures relative humidity; place it at iguana level, away from the water dish |
| Dimming thermostat | Controls heat lamps and prevents overheating |
| On/off or pulse thermostat | Controls ceramic heat emitters and heat panels |
| Plug-in timer | Keeps the 12-hour day-night light cycle consistent |
Stick-on dial thermometers and hygrometers are often inaccurate. Digital tools are more reliable, and it is worth checking readings in several places, especially in tall enclosures where the top can be much warmer than the bottom.
Signs Your Iguana Is Too Hot or Too Cold
| Too cold | Too hot |
|---|---|
| Sluggish, inactive or slow to react | Open-mouth breathing (gaping) while basking |
| Poor appetite or undigested food in droppings | Avoiding the basking area entirely |
| Darker coloring for long periods | Pressing into the coolest corner or lying in water constantly |
| Spending all day under the lamp and still seeming cold | Restlessness or trying to escape |
These signs can also point to illness, so if adjusting temperatures does not help, read our guide to signs of a sick iguana and contact a reptile veterinarian.
Common Mistakes
- Guessing instead of measuring with accurate digital tools.
- Running heat lamps without a thermostat.
- Making the whole enclosure hot, with no cool zone to escape to.
- Using colored night bulbs for warmth, which disrupts sleep.
- Letting humidity crash in winter when the home heating runs.
- Keeping surfaces constantly wet instead of the air humid.
Humidity and temperature also affect shedding. If your iguana struggles to shed, see our iguana shedding guide.
Seasonal Adjustments
Your home's climate changes through the year, so the enclosure needs attention too.
- Winter: room temperatures drop and indoor heating dries the air. Check night temperatures and humidity more often, and add a ceramic heat emitter or humidifier if needed.
- Summer: enclosures can overheat, especially in sunny rooms. Make sure thermostats are working and the cool zone stays cool.
- Air conditioning: can make rooms cool and dry, so recheck both numbers after changing settings.
Planning for Power Outages
A long power cut can chill an iguana quickly in cold weather. Keep a plan ready: insulate the enclosure with blankets (leaving ventilation), move the iguana to the warmest room, and consider a battery backup for essential heat equipment. Avoid open flames and unvented fuel-burning heaters indoors. If an iguana becomes cold, warm it gradually, not with direct high heat.
Frequently Asked Questions
What Temperature Is Too Cold for an Iguana?
Prolonged temperatures below the low 70s °F are too cool for a pet green iguana. Wild iguanas in Florida become stunned and immobile when temperatures fall into the 40s °F, which shows how vulnerable they are to cold.
Do Iguanas Need Heat at Night?
Only if your home lets the enclosure drop below about 70°F. Use a heat source that gives off no light, such as a ceramic heat emitter on a thermostat, and keep all lights off.
What Humidity Do Iguanas Need?
Green iguanas generally need about 70 percent relative humidity or more. Many care sheets recommend 70–90 percent, measured with a digital hygrometer.
How Do I Know My Iguana's Basking Spot Is Hot Enough?
Measure the basking surface with an infrared temperature gun. It should read about 95–100°F where the iguana lies.
Can I Use a Heat Rock for My Iguana?
It is best not to. Heat rocks can cause serious belly burns. Overhead heat lamps on a thermostat are safer and closer to how iguanas warm up in the sun.
Sources: PetMD, Green Iguana Care Sheet; PetPlace, Green Iguana Care; Exotic Direct, Iguana Vivarium Setup.
