Pentland reservoir a big hit with swimmers IT has been one of the best-kept secrets in the city - but now it's becoming one of the hottest hideaways. More and more avid swimmers have been flocking to the Threipmuir Reservoir in the Pentland Hills, where temperatures in the calm blue waters have been hitting 22C. The setting has become a splash hit since members of the Pentland Triathletes began holding training sessions there. Now organisers have been forced to bring extra wetsuits to meetings, such is the demand from first-timers. The temperatures in the water have been put down to the large amount of peat it contains. Frank Tooley, 53, a committee member for the Pentland Triathletes, said: "There's plenty of room for everyone in the reservoir itself. Wednesday, when we train, does seem to be the most popular night. Swimmers are expected to make the most of the Mediterranean-like water temperature today and over the weekend, as the heatwave continues. Today will mark the 14th day in a row that the temperature has reached 24C or higher, as Scotland heads for its driest July since records began in 1910, and its sunniest since 1989. John Whittaker, 53, who lives in Bonnyrigg, and splits his time between coaching swimming and working for Historic Scotland, said: "We're only a few miles from the city centre, but it feels like we're in the middle of the countryside. We've got this beautiful stretch of water and the hills all around. Others taking a dip also spoke highly of the spot, but revealed it did have its dangers. Caroline Davidson, 38, who lives in Loanhead and recently took part in an Iron Man competition, said: "I've been coming down here regularly for about two years now. It's lovely and peaceful. You should never swim in open water unsupervised, but coming down here with a friend is a great way to get some exercise and relieve stress. Every time you look up, all you can see is the beautiful blue sky and the hills. Some weeks there have been between 80 to 100 people here, but it never feels crowded. Also getting ready to take the plunge were Andy Jarvie, 31, and Barry McGuinness, 33, who are also both in training for endurance events. Mr Jarvie, an estate agent from Leith, said: "I love swimming but after spending all day indoors the last thing I want to do sometimes is go in to yet another building to train. When you can come here that's not a problem. For peat's sake There are several reasons why peat-bottomed bodies of water are warmer. David R Cook, of the Atmospheric Research Section at Argonne National Laboratory, near Chicago, said: "Soils that are better at holding water in them, such as clays and peat, may not evaporate as much water and therefore heat up in the sun."