Maurine Kornfield, known by many as Mighty Mo, began swimming competitively in her 60s.Even through the pandemic, the 99-year-old swam six days a week."I just really enjoy swimming," she told KCAL-TV.The pool has been a place for her to keep cool, too.Temperatures in the 80s and 90s were recorded up and down California, with triple-digit highs in deserts, some mountains, noncoastal valley and interior areas.In Southern California, Palm Springs tied the all-time record of 123 degrees, reached only three other times, in 1993 and twice in 1995.The National Weather Service warned of "dangerously hot, potentially life-threatening temperatures" through Saturday in the San Joaquin Valley.Watch the video above to learn more about this story.The Associated Press contributed to this report.