Heatwave

A heatwave is a prolonged period of unusually high temperatures compared with the normal climate of a region and the time of year. There is no single temperature that defines a heatwave everywhere because each country uses thresholds suited to its local climate. Heatwaves often develop when a persistent high-pressure system settles over an area, allowing clear skies and strong sunshine while limiting cloud formation and the movement of cooler air.

Dry soils can make these events even more intense because less of the Sun's energy is used to evaporate water, leaving more energy available to warm the ground and the air. Heatwaves may last for several days or even weeks, affecting both cities and rural areas. Long-lasting heat can have important consequences for people, animals and ecosystems.

High temperatures increase the risk of dehydration, heat exhaustion and heatstroke, especially among older adults, young children and people with chronic illnesses. Crops may suffer from water stress, rivers and lakes can become warmer, and the danger of wildfires often rises when vegetation is dry.

Large cities frequently experience even higher temperatures because buildings and roads store heat, creating what is known as the urban heat island effect. Scientists have found that climate change is making heatwaves more frequent, longer-lasting and more intense in many parts of the world, making early warnings and heat protection measures increasingly important.