LONDON: Much of western Europe baked under a “heat dome” Wednesday as temperatures soared toward 40 degrees Celsius in places, and weather agencies warned that the extreme conditions could endanger lives across countries, many of which have limited air conditioning.

France recorded its hottest-ever day for the second day running. The Meteo France weather agency said the country’s national thermal indicator — an average of temperatures measured at 30 weather stations — hit a new record of 30 C, the latest in a series of never-before-registered highs. The mercury surpassed 40 C in some locations, including in Paris.

The French weather agency put three-quarters of the country under a red alert for extreme heat starting at midday Thursday until the same time Friday. The warning encompassed tens of millions of people. In the usually temperate Brittany region of northwest France, a heat-related equipment failure knocked out power to tens of thousands of households that had to endure without electric fans.

Meanwhile, the UK recorded its hottest June day, with 36.1 C (96.9 F) reported at Gosport in southern England. The national weather forecaster issued a red alert for heat in much of central and southern England, as well as Wales.