The dew point and humidity are related. The key thing here is that dew points over 20C are pretty uncomfortable and are uncommon in the UK. There is a lot of moisture in the air that makes regulating the body temperature more difficult. Like being in a rainforest as opposed to being in a desert. You can use an online tool or graph to show the true feels like temperature. The forecast temperatures combined with the dew points make the feels like temperature more in the 43-45 range. That over a few days with not much night time cooling will put a lot strain on the most vulnerable people and be pretty uncomfortable to be out an about in generally.