The weather has been very changeable over the past few weeks, with rain, hail, cold temperatures, and sunny days. But the BBC Weather says some parts of England could see a heatwave this weekend. Temperatures could rise over the next few days and reach 28C by Saturday. This is just in time for some schools to start their half-term break. Some areas saw record rainfall in January. The temperature rise could see the south-east of England reach 28C by Saturday, which could be the hottest day of the year so far. Not everywhere will be the same temperature, but many places could reach 20-26C. The BBC Weather says Friday and Sunday could be very hot. But the hot weather doesn't mean no rain - there could be rain in Scotland, Wales, and the west of England on Saturday, and in southern England on Sunday. The reason for the hot weather is a change in wind direction. Last week was cold because the wind was coming from the north, but this week the wind is coming from the south-west. The Met Office defines a heatwave as at least three days of unusually hot weather for the time of year. But this can vary depending on which part of the country you are in. For example, it could be 28C in Greater London, but 25C in Northern Ireland. The BBC Weather says some places could meet the definition of a heatwave on Friday, Saturday, and Sunday, with the most likely places being Herefordshire and Worcestershire. But if it rains over the bank holiday weekend, it could get cooler. Did you know? Heatwaves are a big threat to human health. It's essential to drink plenty of water to control your body temperature in hot weather. You should also use sunscreen to protect yourself from the sun. Heatwaves are also important for the environment. Hot weather can affect plants and animals. Heatwaves are also important for the economy. Hot weather can affect farming and tourism.