The Discomfort Index combines air temperature and relative humidity into one number. It is commonly used as a simple reference for how warm or muggy the air may feel to people. This page calculates it using temperature in °C and relative humidity in %.
The background bands provide a quick visual guide, ranging from cooler conditions through comfortable, uncomfortable, and very uncomfortable conditions. The index is mainly useful for heat and humidity, however. Values are still calculated during cold weather, but they should not be treated as a precise measure of winter cold or cold stress.
People do not all experience the same conditions in the same way. Wind, direct sunlight, clothing, activity level, health, and individual sensitivity are not included in this calculation. For that reason, it is better to read the purple Discomfort Index line together with the temperature and humidity lines rather than relying on the background bands alone.
The Discomfort Index is a measure of human comfort, not plant comfort or plant stress. Still, the temperature and humidity behind the index are part of the environment around plants. When thinking about plants, those measurements are more useful when considered together with air VPD, light, wind, substrate moisture, root-zone conditions, and the plant’s species and current condition.
This page is a simple outdoor-comfort reference. It is not a medical advisory, a heat-warning service, a weather forecast, or a substitute for WBGT or other dedicated heat-stress measures.
The source data come from one observation point at my horticultural facility in Fushimi, Kyoto, Japan. They are useful as a local reference, but they do not represent conditions across Kyoto as a whole.