Paramedics have issued a warning to Sydneysiders to keep cool and stay hydrated ahead of an intense heatwave. Temperatures in Sydney are set to exceed 30 degrees by Friday, while those in Western Sydney and regional areas are being told to brace for temperatures in excess of 40 degrees. Friday's scorcher will mark the warmest weather Sydney has experienced since February. Alan Morrison, Chief Superintendent of NSW Ambulance, said Australians should keep a close eye out for the symptoms of heat-related stress. "It's important that people are alert to the symptoms associated with heat exhaustion in themselves or others, especially young children and the elderly," said Supt Morrison. "These include nausea, faintness, dizziness, loss of appetite, weakness, headache, and vomiting. "Heat can kill which is why it's so important to stay hydrated and look out for the elderly the young and pets." NSW Ambulance figures from last summer show from the 1st of December 2017 to 31st of March 2018 paramedics treated 4451 patients for dehydration and 227 people suffering from heat exhaustion. NSW Ambulance aeromedical teams were called to 1536 jobs, a number of which involved patients suffering from severe heat exhaustion and requiring helicopter transport to the hospital. Data from the Bureau of Meteorology (BOM) shows heat is already building in NSW's west and will continue to intensify over the next few days. "Temperatures in the west are likely to sit around the 40-degree mark for several days. Western Sydney can expect to reach the high thirties on Thursday and Friday," said BOM's NSW/ACT manager of weather services, Jake Phillips. "One of the characteristics of heatwaves is not just hotter maximum temperatures but also hotter minimums." Mr. Phillips warned that because this Friday's looming heatwave was the first of the season it could have a greater impact on the community that those in the middle of summer. Superintendent Morrison again warned residents not to leave children or animals inside a car, as temperatures on a 35-degree day can easily exceed 47 degrees inside the vehicle. "Never leave children or animals in a car unattended even if you think it's only going to be for a minute," said Supt Morrison.