Humidity & Temperature Checker

Why temperature and humidity matter

Houseplants are mostly tropical plants living a long way from home. In their native forests the temperature rarely drops below 65°F (18°C) and the air is often 50 to 70 percent humidity. The average heated home in winter sits at 68 to 72°F — warm enough — but the humidity can fall to 20 or 30 percent, which is desert air for a monstera or a fern. Cold is the other danger: most tropical houseplants suffer below 55°F (13°C), and a plant left against a cold window on a frosty night can be damaged even if the room itself feels fine. Temperature and humidity also interact: warm air holds more moisture, so the same room feels drier to a plant when the heating is on, and a plant that is too cold uses less water, so it is easier to overwater in winter. Checking both numbers together, as this tool does, is more useful than checking either one alone.

Reading the results

If both readings sit inside the usual range for the plant group, your room is fine — the best thing you can do is keep conditions steady, because most houseplants dislike sudden change more than slightly imperfect conditions. If the temperature is too low, moving the plant away from draughts and cold glass usually helps more than turning the heating up; a plant on a windowsill can be 10 degrees colder than the same plant a metre into the room. If the temperature is too high, shade and airflow help more than anything else. If the humidity is too low — the most common problem in winter — grouping plants together raises the local humidity, a tray of pebbles and water under the pot adds moisture as it evaporates, and a small humidifier is the most reliable fix of all. Misting helps for a few minutes and then the air is dry again, so do not rely on it alone. If the humidity is too high, airflow is the answer: a fan on low or an open vent stops stagnant air and reduces the risk of mould on leaves and soil.

Common signs of the wrong conditions

Brown, crispy leaf tips and edges are the classic sign of dry air, and they are very common on calatheas, ferns and peace lilies in heated rooms. Leaves that droop or curl in a warm room are often reacting to heat and low humidity together. A plant that drops leaves after a cold snap, or that arrived home from a shop in winter and promptly sulked, has usually had a cold shock. Mould on the soil surface and soft, dark patches on leaves point to air that is too humid and still — improve airflow and let the soil dry a little more between waterings. Note that brown tips can also come from salts in tap water or from over-fertilising, so if you fix the humidity and the problem continues, try rainwater or letting tap water stand overnight. For the watering side of the same problem, use the watering calculator and the watering schedule generator.

Measuring properly

A small digital hygrometer costs little and gives both numbers at once — put it where the plants actually are, not on the other side of the room, because temperature and humidity vary a surprising amount within a single room. Check at different times of day and in different seasons: a room that is comfortable in summer can be dry and draughty in winter. And remember that the plant group is a guide, not a rule — individual species vary, so when you know the exact plant, check its care guide in the houseplant care guides. To check the light in the same spot, use the sunlight calculator and the grow-light calculator.