Summer is making a comeback in Southern California with autumn temperatures soaring nearly 20 degrees above normal. National Oceanic and Atmospheric Administration (NOAA) data show a widespread heat wave across the region with temperatures of between 90 and 102 degrees Fahrenheit. A 98-degree reading in downtown Los Angeles Thursday was the highest October recording since 1999, according to the National Weather Service and Weather Underground. \"Weather has natural extremes, but these natural extremes are now occurring in an atmosphere that has more heat and moisture in it due to global warming,\" Jeff Masters, Weather Underground\'s Director of Meteorology told Xinhua via email. \"Global warming has also altered the jet stream, which affects the path of storm systems,\" he said. \"When we get a naturally extreme year like this year, the extremes can get increased by the fact they are occurring in an atmosphere that has been changed by global warming.\" \"This results in unprecedented weather events where records get smashed by a large amount, not just barely broken. Extreme years like 2011 will occur with increasing frequency in coming decades,\" Masters said. \"In some parts of the world, the impacts of global warming are already apparent, and people should be prepared for more extreme weather in the future.\" The Southern California Association of Governments warns that, by the year 2100, Southern California\'s overall temperature will rise by four to 10 degrees Fahrenheit. Heat waves \"will likely intensify and last longer.\" In the same time frame, water levels along the coast will rise by 1.5 feet, even as precipitation continues to be erratic and unpredictable. This will most likely lead to water shortages, according to local media. Many people stayed out of sun or used umbrellas and sunscreen to protect themselves from the sun\'s rays. But despite the heat, Occupy Los Angeles protesters remained camped out in the heat in front of City Hall, downtown Los Angeles. \"During excessive heat events, people should take necessary precautions to avoid heat-related symptoms, heat stress, heat exhaustion, or possibly heat stroke,\" Eric Boldt, Warning Coordination Meteorologist for the National Weather Service Los Angeles/Oxnard told Xinhua via email.