A frog feels winter through its skin and its water
A green tree frog is more exposed to winter conditions than a scaly reptile in the same room. Its permeable skin takes in moisture and whatever that moisture carries, it breathes partly through that skin, and it regulates its body using the temperature of the air and water immediately around it. In winter, the threats are a tank that cools too far at night, air dried out by home heating, and water quality slipping because a quieter frog draws less attention. Your frog does not need a hot enclosure. It needs a steady one, roughly in the mid-seventies to low eighties, with humidity high enough that it stays active, feeds and soaks as usual.
Gentle, controlled warmth for a small enclosure
Small tanks change temperature quickly, so whatever heat you use must be controlled and checked. A thermometer at the frog's perch height, read morning and evening, tells you whether night-time heating in your home is leaving the enclosure cold for hours. If you use a heat source, it should raise the enclosure gently and create a slightly warmer side rather than baking the whole tank, and it must never be something the frog can press against and burn. Position the tank away from cold window glass and draughts, and not directly above a radiator, where each heating cycle pushes temperatures up and then lets them fall. Stability, more than any single perfect reading, is what keeps a tree frog feeding through winter.
Moisture, misting and the soaking bowl
Winter air indoors can be surprisingly dry, and a tree frog responds by becoming less active and shedding poorly. Mist with dechlorinated water to restore droplets on leaves and glass, and keep the soaking bowl clean and filled with the same safe water, changed daily or whenever it is fouled. Chlorine and chloramine in untreated tap water matter to amphibians in a way they do not to most reptiles, so water treatment is a winter essential, not a detail. Keep substrate damp rather than sodden, and remove uneaten insects, which die faster in a warm, humid tank and pollute it. If the enclosure smells sour, that is a cleaning signal, not something to mask with extra misting.
Feeding and behaviour through the cold months
Offer food in the evening, when your frog wakes, and keep a simple note of what was taken. A modest slowing on the coldest weeks can follow slightly lower temperatures, but a frog that stops calling, stops soaking, sits with eyes closed during active hours or loses condition needs the setup checked first and a vet with amphibian experience if the signs continue. Keep handling to almost none in winter: dry, warm hands damage delicate skin, and any handling should be with wet, clean, product-free hands or gloves. Keep soap, hand cream and aerosol sprays away from the enclosure entirely, because residues travel through skin.
Quiet checks that catch winter drift early
Build a brief evening round: glance at the thermometer, check the bowl, mist if leaves are dry, count whether last night's food was eaten, and look at the frog's posture on its perch. Two minutes of looking catches the slow drift that actually harms amphibians in winter, which is rarely a single cold night and usually a week of slightly wrong conditions nobody noticed. If a reading or a change in your frog leaves you unsure whether it matters, that is the moment to ask rather than wait. For those uncertain winter moments, KinsLe's Kimmy is built into the app as an assistant you can ask for guidance in the moment, and what you learn can stay alongside your green tree frog's profile for the next check.