Omega block: What is the weather phenomenon driving Europe’s heatwave

Published 26 June 2026 · europe

Europe is reeling under an intense heatwave, with health alerts issued across western and central regions as temperatures surge to record levels. With the continent

Europe is reeling under an intense heatwave, with health alerts issued across western and central regions as temperatures surge to record levels. With the continent warming at more than twice the global average, the World Meteorological Organization has cautioned that Europe faces a rising risk of prolonged spells of extreme heat. Among the drivers of such extremes are atmospheric and circulation patterns that trap hot air over a region for days, causing temperatures to rise steadily. The ongoing heatwave in western Europe, which has claimed more than 40 lives in France alone, is being sustained by a weather pattern known as an omega block. Omega block The heatwave in Europe is being driven by an omega block, pushing temperatures to unusually high levels, according to the Reuters Climate Monitor. The pattern resembles the Greek letter omega, with a bulging ridge of high pressure trapping heat over a region, while cooler conditions persist along its edges. An omega block is a stalled, Ω-shaped wind pattern that confines air within it, preventing ventilation. This leads to a build-up of heat, resulting in oppressive conditions. The trapped heat prevents cooling even at night. Unlike a typical moving heatwave, stagnant air within such a system can also trap pollutants, leading to poor air quality. Climate variability, including phenomena such as La Nina and El Nino, may intensify these effects.

In the coming days, the hot conditions are expected to extend to parts of eastern Europe as well. It remains uncertain how long the present heatwave, driven by an omega block that allows temperatures to build up over successive days, will persist. Phenomenon behind omega block An omega block takes the shape of the Greek letter Ω, with a bulge of warm, settled high pressure held between two cooler low-pressure systems. The term “blocking” refers to the way the high-pressure system becomes stationary. Under normal conditions, the jet stream carries weather systems from west to east. During an omega block, this flow is disrupted and can meander sharply north and south, isolating pressure systems. Weaker steering winds and reduced temperature contrasts in the atmosphere contribute to these slow-moving patterns. As a result, hot and still air remains over the same region. Omega blocks typically last between three and 10 days, but can sometimes persist for weeks. What happens during an omega block Beneath the high-pressure zone at the centre, conditions turn hot and dry. The system suppresses cloud formation, leading to clear skies and uninterrupted sunshine that pushes temperatures higher. Such conditions have prevailed in France and Spain, where temperatures have crossed 40 degrees Celsius. Regions under the flanking low-pressure systems, in contrast, are likely to experience cooler and wetter weather.