Parts of the UK could experience a heatwave with temperatures expected to soar this weekend and next week, the Met Office has warned. The south-east, particularly London and the home counties, could reach 30C on Sunday, Monday and Tuesday. Bright spells are forecast for Sunday, in what the weather forecaster described as a “fine and dry day for many”. Temperatures are expected to reach 25C in the north-east. Yorkshire is the northern limit in terms of the area expected to reach “heatwave criteria”, the Met said, with 25C temperatures continuing into early next week. Saturday is predicted to be sunny with showers, heaviest in parts of Scotland, northern England, Wales and the Midlands, and isolated thunder possible. Heatwave criteria is met when a location records at least three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold, which varies by county. Earlier this month, UK temperatures reached their highest point in the year so far, with 31.9C recorded at St James’s Park in central London. The high pressure will lead to clear skies and sunshine across the UK, the Met Office said, which at this time of year will allow temperatures to gradually rise day on day. However, it is uncertain how long the warmer weather will last. David Hayter, a deputy chief meteorologist at the Met Office, said: “As we go through the weekend, the jet stream will weaken to the west of the UK, generating an area of high pressure that will slowly move in across the UK. “High pressure means the air is sinking from higher in the atmosphere and that brings drier, settled and sunnier weather. There’s a bit more in the way of patchy cloud in Northern Ireland, south and west Scotland and the Northern Isles, so temperatures will be lower there.” The Met Office forecaster Greg Dewhurst warned that despite the warm weather, water temperatures could be much lower. “Be mindful that at this time of year the water’s still pretty cold, around 16, 17, 18C. It’s not like in the Mediterranean, where it’s much warmer,” he said. Tom Morgan, a meteorologist at the Met Office, said the hot weather was owing to the fact that “days are longer at this time of year, we’re only one month past the summer solstice, and when it’s a sunny day, temperatures build because the land retains more heat than it loses by night”.