Mugginess

Mugginess, or the muggy feel of air, describes a weather or indoor condition in which the air feels damp, sticky, and oppressive. It is a perceptual phenomenon resulting from the combination of moisture in the air, temperature, and airflow, and it is not defined by a single precise measurement. Nevertheless, humidity and dew point are the metrics most closely associated with the sensation of mugginess.

Causes and indicators: High relative humidity coupled with warm or hot temperatures tends to produce a muggy environment. The dew point provides a more reliable signal than relative humidity alone; when the dew point is around 18°C (64°F) or higher, the air often feels humid, and above about 20°C (68°F) it can feel oppressive. Poor air circulation, stagnant air, and urban heat islands can amplify the sensation by reducing evaporative cooling from the skin.

Effects on people: Mugginess can lead to discomfort, reduced ability to regulate body temperature through sweating, and poorer sleep or work performance. In hot conditions, muggy air increases the risk of heat-related illness, particularly for elderly individuals, children, and people with chronic health conditions such as asthma or cardiovascular disease. Prolonged high humidity can promote mold growth indoors if ventilation is inadequate.

Mitigation and adaptation: Measures to reduce mugginess include air conditioning or dehumidification, improving ventilation, using fans to promote air movement, and reducing sources of indoor moisture. Wearing lightweight, breathable clothing and staying hydrated can help, as can scheduling outdoor activities for cooler parts of the day. Building design and urban planning that promote airflow and reduce heat buildup can lessen the intensity of muggy conditions.