Why this heatwave feels worse than the last one

Image source, Getty Images Image caption, For many, the high temperatures will feel worse than they are By Simon King Lead Weather Presenter Published 17 minutes ago June temperature records are set to be broken this week as the second heatwave of the year grips England and Wales. The mercury is set to reach into the mid- to high 30s Celsius, making for a few very uncomfortable days and nights. But for many of us, it will feel even hotter. That's down to a combination of factors: an unrelenting heat dome, high humidity, and back-to-back tropical nights. Heat dome is 'driving force' behind heatwave The intense record-breaking heatwave in the UK and Europe has been caused by a static and large area of high pressure – also referred to as a heat dome. This is the "driving force" behind the heatwave, Dr Akshay Deoras, senior research scientist at the University of Reading, told BBC Weather. This weather pattern results in air sinking down through the atmosphere where it heats up and gets drier, resulting in more sunshine heating the ground. During the May heatwave, the centre of the heat dome was over the UK which resulted in dry and very warm air. This week, it has originated in the sub-tropics and been centred more over France where temperatures have soared into the 40s Celsius. As it has shifted slightly further north and to the east, the result has been a south-easterly airflow causing hotter and moister air to spread into the UK. This moist air results in much higher humidity and adds significantly to the heat stress. Dr Deoras said: "This is not just a heatwave, it is a heat-dome driven furnace that will grip most of the southern UK and push temperatures into truly exceptional territory." High humidity prevents the body from cooling down The hottest areas of the UK - namely southern England and parts of Wales - will see the thermometer rise to 38 or 39C, and this becomes particularly uncomfortable when you factor in the humidity. Humidity is a measure of how much moisture is in the air. During hot weather our body controls our internal temperature by sweating and as the sweat is evaporated from our skin, it cools the air directly next to us, making us feel cooler. If the air is more humid, the sweat from our skin cannot evaporate and cool us down as effectively as it would do if the air was dry. Meteorologists can calculate therefore how the combination of air temperature and humidity feels – as a "feels like" temperature. While the air temperature in the coming days might be 35C for example, it may actually "feel" more like it's 41C. With temperatures nudging 40C, there have been some comparisons to the historic heatwave of July 2022 when the UK recorded 40C for the first time. But during that heatwave the air was very dry. So, while headline temperatures were higher then, this June's heatwave will feel hotter and potentially have more health impacts as a result of the humidity. UK set for hottest June day on record as searing heat continue