OK, it may not be Summer yet on the calendar…but try telling that to Mother Nature: Excessive heat warnings are set to expire this weekend after daily temperature records have been set across the US Southwest. Extreme temperatures are expected to continue in California, Nevada and Arizona into Saturday. An excessive heat warning in Las Vegas will expire Saturday night with temperatures remaining around 115F (46.1) on Saturday and dropping to 112F (44.4C) on Sunday. Similar to the trend throughout last week, temperatures will remain high at night hovering around the low 80s. On Thursday, the heat hit 113F (45C) in Phoenix. Record-breaking temperatures led to 11 people taken to the hospital while waiting to attend a Donald Trump rally on Wednesday. Phoenix will see some slight relief after the heat warning expires Friday night, but the high temperature remains in triple digits for Saturday at 108F (42.2C) and 104F (40C) on Sunday. National Weather Service (NWS) alerts remain in place on Friday for the wider area, covering a population of around 20 million people. The heat marks the first round of dangerous temperatures this season with the possibility of excessive heat persisting into next week for some areas, according to the NWS Weather Prediction Centre. Scientists say extreme weather events are becoming more frequent and intense as a result of climate change. Although the official start of summer is still two weeks away, NWS has advised people in the affected areas to limit outdoor activity and stay hydrated. It…