26th Annual Pinnacle Peak Pedalers Potluck

When I arrived at the Usery Mountain Regional Park for the 2015 version of the New Years Day Pinnacle Peak Peddlers potluck at 9:00 A.M. the thermometer registered 34º. When I left at 1:15 P.M., the thermometer showed 42”. What
transpired in that 8º window?